-
Did Doberiener's triads also exist in the columns of NewIands' octaves ? Compare and find out.
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What were the limitations of Doberemer's classification ?
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What were the limitations of Newlands' Law of Octaves?
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Use Mendeleev's periodic table to predict the formulae for the oxides of the following elements:
K, C, Al, Si, Ba.
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Besides gallium, which other elements have since been discovered that were left by Mendeleev in his periodic table ? (any two)
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What were the criteria used by Mendeleev in creating his periodic table ?
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Why do you think the noble gases are placed in a separate group ?
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How could the modern periodic table remove various anomalies of Mendeleev periodic table ?
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Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice ?
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Name:
(a) three elements that have a single electron in their outermost shells.
(b) two elements that have two electrons in their outermost shells.
(c) three elements with filled outermost shells.
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(a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas.
Is there any similarity in the atoms of these elements?
(b) Helium is an un reactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
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In the modem periodic table, which are the metals among the first ten elements?
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By considering their position in the periodic table, which one of the following elements would you expect to have maximum metallic characteristics ? Ga, Ge, As, Se, Be
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Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic table ?
(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their elements more easily
(d) The oxides become more acidic.
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Element X forms a chloride with
the formula
which
is a solid with high melting point. X would most likely to be in the same
group of the periodic table as :
(a) Na
(b) Mg
(c)
Al (d) Si
-
Which element has
(a) two shells, both of which are completely filled with electrons ?
(b) the electronic configuration 2, 8, 2 ?
(c) a total of three shells, with four electrons in its valence shell ?
(d) a total of two shells, with three electrons in its valence shell ?
(e) twice as many electrons in its second shell as in its first shell ?
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(a) What property do all electrons in the same column of the periodic table as boron have in common ?
(b) What property do all elements in the same column of the periodic table as fluorine have in common ?
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An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element ?
(b) To which of the following elements would it be chemically similar? (Atomic numbers are giving in parentheses).
N(7), F(9), P(15), Ar(18)
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The position of three elements A, B and C in the periodic table are shown below :
Group 16 Group 17
- -
- A
- -
B C
(a) State whether A is metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be largeror smaller in size than B ?
(d) Which type of ion, cation or anion will be formed by the element A ?
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Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write then-electronic configuration. Which of these will be more electronegative and why?
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How does the electronic configuration of an atom relate to its position in the modern periodic table?
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In the modern periodic table, calcium (atomic number 20) is surrounded by elements with atomic number 12, 19, 21, and 38. Which of these have physical and chemical properties resembling calcium?
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Compare and contrast the arrangement of elements in Mendeleev's periodic table and the modern periodic table.
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question_answer24)
Upto which element,
the law of octaves was found to be applicable?
(a) Oxygen (b)
Calcium (c) Cobalt (d)
Potassium
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question_answer25)
According to
Mendeleev's periodic law, the elements were arranged in the periodic table in
the order of
(a) increasing
atomic number (b) decreasing atomic number
(c)
increasing atomic masses (d) decreasing
atomic masses
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question_answer26)
In
Mendeleev's periodic table, gaps were left for the elements to be discovered
later. Which of the following elements found a place in the periodic table
later?
(a)
Germanium (b) Chlorine (c) Oxygen (d)
Silicon
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question_answer27)
Which of the
following statement(s) about the modern periodic table are incorrect?
(i) The
elements in the modern periodic table are arranged on the basis of their
decreasing atomic numbers.
(ii) The
elements in the modern periodic table are arranged on the basis of their
increasing atomic masses.
(iii)
Isotopes are placed in adjoining group(s) in the periodic table.
(iv) The
elements in the modern periodic table are arranged on the basis of their
increasing atomic number.
(a) Only
(i) (b) (i), (ii) and (iii) (c) (i), (ii)
and (iv) (d) Only (iv)
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question_answer28)
Which of the
following statements about the modern periodic table is correct?
(a) It has
18 horizontal rows known as periods (b) It has 7 vertical columns rows known
as periods
(c) It has
18 vertical columns known as groups (d) It has 7 horizontal rows known as
groups
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question_answer29)
Which of the
given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30
respectively belong to the same period?
(a) A, B,
C (b) B, C, D (c) A, D,
E (d) B, D, E
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question_answer30)
The elements
A, B, C, D and E have atomic number 9, 11, 17, 12 and13 respectively. Which
pair of elements belong to the same group?
(a) A and
B (b) B and D (c) A and
C (d) D and E
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question_answer31)
Where would
you locate the element with electronic configuration 2, 8 in the modern
periodic table?
(a) Group
8 (b) Group 2 (c) Group 18 (d)
Group 1 0
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question_answer32)
An element which, is
an essential constituent of alt organic compounds belongs to
(a) group
1 (b) group 14 (c) group 15 (d)
group 16
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question_answer33)
Which of the
following is the outermost shell for elements of period 2?
(a) K shell (b)
L shell (c) M shell (d) N
shell
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question_answer34)
Which one of the
following elements exhibit maximum number of valence electrons?
(a)
Na (b) Al (c)
Si (d) P
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question_answer35)
Which of the
following gives the correct increasing order of the atomic radii of 0, F and N?
(a) O, F,
N (b) N, F, O (c) O, N, F (d)
F, O, N
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question_answer36)
Which among
the following elements has the largest atomic radii?
(a) Na (b)
Mg (c) K (d)
Ca
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question_answer37)
Which of the
following elements would lose an electron easily?
(a) Mg (b)
Na (c) K (d)
Ca
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question_answer38)
Which of the
following elements does not lose an electron easily?
(a) Na (b)
F (c) Mg (d)
Al
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question_answer39)
Which of the
following are the characteristics of isotopes of an element?
(i) Isotopes
of an element have same atomic masses.
(ii) Isotopes
of an element have same atomic number.
(iii) Isotopes
of an element show same physical properties.
(iv) Isotopes
of an element show same chemical properties.
(a) (i),
(iii) and (iv) (b) (ii), (iii) and (iv) (c) (ii) and (iii) (d)
(ii) and (iv)
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question_answer40)
Arrange the
following elements in the order of their decreasing metallic character Na, Si,
Cl, Mg, Al.
(a)
(b)
(c)
(d)
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question_answer41)
Arrange the
following elements in the order of their in creasing non-metallic character Li,
O, C, Be, F
(a)
(b)
(c) (d)
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question_answer42)
What type of
oxide would Eka-auminium form?
(a)
(b)
(c)
(d)
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question_answer43)
Three elements B, Si
and Ge are
(a) metals (b)
non-metals
(c) metalloids (d)
metal, non-metal and metalloid respectively
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question_answer44)
Which of the
following elements will form an acidic oxide?
(a) An
element with atomic number 7 (b) An element with atomic
number 3
(c) An
element with atomic number 12 (d) An element with atomic
number 19
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question_answer45)
The element
with atomic number 14 is hard and forms acidic oxide and a covalent halide. To
which of the following categories does the element belong?
(a) Metal (b)
Metalloid (c) Non-metal (d)Left-hand
side element
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question_answer46)
Which one of the
following depict the correct representation of atomic radius (r) of an atom?
(a) (i) and
(ii) (b) (ii) and (iii) (c) (iii) and
(iv) (d) (i) and (iv)
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question_answer47)
Which one of the
following does not increase while moving down the group of the periodic table?
(a) Atomic
radius (b) Metallic character (c) Valence (d)
Number of shells in an element
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question_answer48)
On moving
from left to right in a period in the periodic table, the size of the atom
(a)
increases (b)
decreases
(c) does not
change appreciably (d) first decreases and then
increases
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question_answer49)
Which of the
following set of elements is written in order of their increasing metallic
character?
(a) Be, Mg,
Ca (b) Na, Li, K (c) Mg, Al, Si (d)
C, O, N
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question_answer50)
The three elements
A, B and C with similar properties have atomic masses X, Y and Z respectively.
The mass of Y is approximately equal to the average mass of X and Z. What is
such an arrangement of elements called as? Give one example of such a set of
elements.
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question_answer51)
Elements
have been arranged in the following sequence on the basis of their increasing
atomic masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K.
(a) Pick two
sets of elements which have similar properties.
(b) The
given sequence represents which law of classification of elements?
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question_answer52)
Can the
following groups of elements be classified as Dobereiner's triad?
(a)
(b) 
Atomic mass
of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40
Explain by
giving reason.
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question_answer53)
In
Mendeleev's periodic table, the elements were arranged in the increasing order
of their atomic masses. However, cobalt with atomic mass of 58.93 amu was
placed before nickel having an atomic mass of58.71 amu. Give reason for the
same.
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question_answer54)
'Hydrogen
occupies a unique position in modern periodic table', justify the statement.
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question_answer55)
Write the
formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted
by Mendeleev.
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question_answer56)
Three
elements A, B and C have 3, 4 and 2electrons respectively in their outermost
shell. Give the group number to which they belong in the modern periodic table.
Also, give their valencies.
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question_answer57)
If an
element X is placed in group 14, what will be the formula and the nature of
bonding of its chloride?
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question_answer58)
Compare the
radii of two species X and Y. Give reasons for your answer.
(a) X has 12
protons and 12 electrons
(b) has 12
protons and 10 electrons
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question_answer59)
Arrange the
following elements in increasing order of their atomic radii.
(a)
(b)
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question_answer60)
Identify and
name the metals out of the following elements whose electronic configurations
are given below.
(a)2, 8, 2 (b)2,8,1 (c)
2, 8, 7 (d)2,1
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question_answer61)
Write the formula of
the product formed when the element. A (atomic number 19) combines with the
element B (atomic number 17). Draw its electronic dot structure. What is the
nature of the bond formed?
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question_answer62)
Arrange the
following elements in the increasing order of their metallic character Mg, Ca,
K, Ge, Ga.
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question_answer63)
Identify,
the elements with the following property and arrange them in increasing order
of their reactivity.
(a) An
element which is a soft and reactive metal.
(b) The metal
which is an important constituent of limestone.
(c) The
metal which exists in liquid state at room temperature.
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question_answer64)
Properties
of the elements are given below. Where would you locate the following elements
in the periodic table?
(a) A soft
metal stored under kerosene.
(b) An
element with variable (more than one) valency stored under water.
(c) An
element which is tetravalent and forms the basis of organic chemistry.
(d) An
element which is an inert gas with atomic number 2.
(e) An
element whose thin oxide layer is used to make other elements corrosion resistant
by the process of '"an odising".
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question_answer65)
An element is placed
in 2ndgroup and 3rdperiod of the periodic table, burns in
presence of oxygen to form a basic oxide.
(a) Identify
the element.
(b) Write
the electronic configuration.
(c) Write a
balanced equation when it burns in the presence of air.
(d) Write a
balanced equation when this oxide is dissolved in water
(e) Draw the
electron dot structure for the formation of this oxide.
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question_answer66)
An element X
(atomic number 17) reacts with an element Y (atomic number 20) to form a
divalent halide.
(a) Where in
the periodic table are elements X and Y placed?
(b) Classify
X and Y as metal (s), non-metal (s) or metalloid (s).
(c) What
will be the nature of oxide of element Y? Identify the nature of bonding in the
compound formed.
(d) Draw the
electron dot structure of the divalent halide.
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question_answer67)
Atomic
number of a few elements are given below 10, 20, 7, 14
(a) Identify
the elements.
(b) Identify
the group number of these elements in the periodic table.
(c) Identify
the periods of these elements in the periodic table.
(d) What
would be the electronic configuration for each of these elements?
(e) Determine
the valency of these elements.
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question_answer68)
Complete the following
crossword puzzle (Figure).
Across
(1) An
element with atomic number 12.
(2) Metal
used in making cans and member of group 14.
(3) A
lustrous non-metal which has 7 electrons in its outermost shell.
Down
(2) Highly
reactive and soft metal which imparts yellow colour when subjected to flame and
is kept in kerosene.
(5) The
first element of second period.
(6) An
element which is used in making flurescent bulbs and is second member of group
18 in the modern periodic table.
(7) A
radioactive element which is the last member of halogen family.
(8) Metal
which is an important constituent of steel and forms rust when exposed to moist
air.
(9) The first
metalloid in modern periodic table whose fibres are used in making bullet-proof
vests.
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question_answer69)
(a) In this ladder
(Figure) symbols of elements are jumbled up. Rearrange these symbols of
elements in the increasing order of their atomic numbers in the periodic table.
(b) Arrange them in
the order of their group also.
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question_answer70)
Mendeleev predicted
the existence of certain elements not known at that time and named two or them
as Eka-silicon and Eka-aluminium.
(a) Name the
elements which have taken the place of these elements.
(b) Mention
the group and the period of these electron in the modern periodic table.
(c) Classify
these elements as metals, nonmetals or metalloids.
(d) How many
valence electrons are present in each one of them?
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question_answer71)
.
(a)
Electropositive nature of the element (s) increases down the group and
decreases across the period.
(b)
Electronegativity of the element decreases down the group and increases across
the period.
(c) Atomic size
increases down the group and decreases across a period (left to right),
(d) Metallic
character increases down the group and decreases across a period.
On the basis
of' the above trends of the periodic table, answer the following about the
electron with atomic numbers 3 to 9.
(a) Name the
most electropositive element among them.
(b) Name the
most electropositive element.
(c) Name of
the element with smallest atomic size.
(d) Name me
element which is a metalloid.
(e) Name the
element which shows maximum valency.
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question_answer72)
An element X
which is a yellow solid at room temperature shows catenation arid allotropy. X
forms two oxides which are also formed during the thermal, decomposition of
ferrous sulphate crystals and are the major air pollutant
(a) Identify
the element X.
(b) Write the
electronic configuration of X.
(c) Write
the balanced chemical equation for the thermal decomposition of ferrous
sulphate crystals?
(d) What
would be the nature (acidic/basic) of oxides formed?
(e) Locate
the position of the element in the modern periodic table.
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question_answer73)
An element X
of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in
presence of the catalyst to form a compound, ammonia which has a characteristic
pungent smell.
(a) Identify
the element X. How many valence electrons does it have?
(b) Draw the
electron dot structure of the diatomic molecule of X. What type of bond is
formed in it?
(c) Draw the
electron dot structure for ammonia and what type of bond is formed in it?
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question_answer74)
Which group
of elements could be placed in mendeleev's periodic table without disturbing
the original order? Give reason.
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question_answer75)
Give an account of
the process adopted by Mendeleev for the classification of elements. How did he
arrive at "periodic law"?
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question_answer76)
Upto which element,
the law of octaves was found to be applicable?
(a) Oxygen (b)
Calcium (c) Cobalt (d)
Potassium
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question_answer77)
According to
Mendeleev's periodic law, the elements were arranged in the periodic table in
the order of
(a) increasing
atomic number (b) decreasing atomic number
(c)
increasing atomic masses (d) decreasing
atomic masses
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question_answer78)
In
Mendeleev's periodic table, gaps were left for the elements to be discovered
later. Which of the following elements found a place in the periodic table
later?
(a)
Germanium (b) Chlorine (c) Oxygen (d)
Silicon
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question_answer79)
Which of the
following statement(s) about the modern periodic table are incorrect?
(i) The
elements in the modern periodic table are arranged on the basis of their
decreasing atomic numbers.
(ii) The
elements in the modern periodic table are arranged on the basis of their
increasing atomic masses.
(iii)
Isotopes are placed in adjoining group(s) in the periodic table.
(iv) The
elements in the modern periodic table are arranged on the basis of their
increasing atomic number.
(a) Only
(i) (b) (i), (ii) and (iii) (c) (i), (ii)
and (iv) (d) Only (iv)
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question_answer80)
Which of the
following statements about the modern periodic table is correct?
(a) It has
18 horizontal rows known as periods (b) It has 7 vertical columns rows known
as periods
(c) It has
18 vertical columns known as groups (d) It has 7 horizontal rows known as
groups
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question_answer81)
Which of the
given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30
respectively belong to the same period?
(a) A, B,
C (b) B, C, D (c) A, D,
E (d) B, D, E
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question_answer82)
The elements
A, B, C, D and E have atomic number 9, 11, 17, 12 and13 respectively. Which
pair of elements belong to the same group?
(a) A and
B (b) B and D (c) A and
C (d) D and E
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question_answer83)
Where would
you locate the element with electronic configuration 2, 8 in the modern
periodic table?
(a) Group
8 (b) Group 2 (c) Group 18 (d)
Group 1 0
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question_answer84)
An element which, is
an essential constituent of alt organic compounds belongs to
(a) group
1 (b) group 14 (c) group 15 (d)
group 16
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question_answer85)
Which of the
following is the outermost shell for elements of period 2?
(a) K shell (b)
L shell (c) M shell (d) N
shell
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question_answer86)
Which one of the
following elements exhibit maximum number of valence electrons?
(a)
Na (b) Al (c)
Si (d) P
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question_answer87)
Which of the
following gives the correct increasing order of the atomic radii of 0, F and N?
(a) O, F,
N (b) N, F, O (c) O, N, F (d)
F, O, N
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question_answer88)
Which among
the following elements has the largest atomic radii?
(a) Na (b)
Mg (c) K (d)
Ca
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question_answer89)
Which of the
following elements would lose an electron easily?
(a) Mg (b)
Na (c) K (d)
Ca
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question_answer90)
Which of the
following elements does not lose an electron easily?
(a) Na (b)
F (c) Mg (d)
Al
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question_answer91)
Which of the
following are the characteristics of isotopes of an element?
(i) Isotopes
of an element have same atomic masses.
(ii) Isotopes
of an element have same atomic number.
(iii) Isotopes
of an element show same physical properties.
(iv) Isotopes
of an element show same chemical properties.
(a) (i),
(iii) and (iv) (b) (ii), (iii) and (iv) (c) (ii) and (iii) (d)
(ii) and (iv)
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question_answer92)
Arrange the
following elements in the order of their decreasing metallic character Na, Si,
Cl, Mg, Al.
(a) (b)
(c) (d)
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question_answer93)
Arrange the
following elements in the order of their in creasing non-metallic character Li,
O, C, Be, F
(a) (b)
(c) (d)
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question_answer94)
What type of
oxide would Eka-auminium form?
(a) (b) (c) (d)
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question_answer95)
Three elements B, Si
and Ge are
(a) metals (b)
non-metals
(c) metalloids (d)
metal, non-metal and metalloid respectively
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question_answer96)
Which of the
following elements will form an acidic oxide?
(a) An
element with atomic number 7 (b) An element with atomic
number 3
(c) An
element with atomic number 12 (d) An element with atomic
number 19
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question_answer97)
The element
with atomic number 14 is hard and forms acidic oxide and a covalent halide. To
which of the following categories does the element belong?
(a) Metal (b)
Metalloid (c) Non-metal (d)Left-hand
side element
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question_answer98)
Which one of the
following depict the correct representation of atomic radius (r) of an atom?
(a) (i) and
(ii) (b) (ii) and (iii) (c) (iii) and
(iv) (d) (i) and (iv)
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question_answer99)
Which one of the
following does not increase while moving down the group of the periodic table?
(a) Atomic
radius (b) Metallic character (c) Valence (d)
Number of shells in an element
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question_answer100)
On moving
from left to right in a period in the periodic table, the size of the atom
(a)
increases (b)
decreases
(c) does not
change appreciably (d) first decreases and then
increases
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question_answer101)
Which of the
following set of elements is written in order of their increasing metallic
character?
(a) Be, Mg,
Ca (b) Na, Li, K (c) Mg, Al, Si (d)
C, O, N
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question_answer102)
The three elements
A, B and C with similar properties have atomic masses X, Y and Z respectively.
The mass of Y is approximately equal to the average mass of X and Z. What is
such an arrangement of elements called as? Give one example of such a set of
elements.
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question_answer103)
Elements
have been arranged in the following sequence on the basis of their increasing
atomic masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K.
(a) Pick two
sets of elements which have similar properties.
(b) The
given sequence represents which law of classification of elements?
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question_answer104)
Can the
following groups of elements be classified as Dobereiner's triad?
(a)
(b)
Atomic mass
of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40
Explain by
giving reason.
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question_answer105)
In
Mendeleev's periodic table, the elements were arranged in the increasing order
of their atomic masses. However, cobalt with atomic mass of 58.93 amu was
placed before nickel having an atomic mass of58.71 amu. Give reason for the
same.
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question_answer106)
'Hydrogen
occupies a unique position in modern periodic table', justify the statement.
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question_answer107)
Write the
formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted
by Mendeleev.
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question_answer108)
Three
elements A, B and C have 3, 4 and 2electrons respectively in their outermost
shell. Give the group number to which they belong in the modern periodic table.
Also, give their valencies.
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question_answer109)
If an
element X is placed in group 14, what will be the formula and the nature of
bonding of its chloride?
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question_answer110)
Compare the
radii of two species X and Y. Give reasons for your answer.
(a) X has 12
protons and 12 electrons
(b) has 12
protons and 10 electrons
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question_answer111)
Arrange the
following elements in increasing order of their atomic radii.
(a)
(b)
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question_answer112)
Identify and
name the metals out of the following elements whose electronic configurations
are given below.
(a)2, 8, 2 (b)2,8,1 (c)
2, 8, 7 (d)2,1
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question_answer113)
Write the formula of
the product formed when the element. A (atomic number 19) combines with the
element B (atomic number 17). Draw its electronic dot structure. What is the
nature of the bond formed?
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question_answer114)
Arrange the
following elements in the increasing order of their metallic character Mg, Ca,
K, Ge, Ga.
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question_answer115)
Identify,
the elements with the following property and arrange them in increasing order
of their reactivity.
(a) An
element which is a soft and reactive metal.
(b) The metal
which is an important constituent of limestone.
(c) The
metal which exists in liquid state at room temperature.
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question_answer116)
Properties
of the elements are given below. Where would you locate the following elements
in the periodic table?
(a) A soft
metal stored under kerosene.
(b) An
element with variable (more than one) valency stored under water.
(c) An
element which is tetravalent and forms the basis of organic chemistry.
(d) An
element which is an inert gas with atomic number 2.
(e) An
element whose thin oxide layer is used to make other elements corrosion resistant
by the process of '"an odising".
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question_answer117)
An element is placed
in 2ndgroup and 3rdperiod of the periodic table, burns in
presence of oxygen to form a basic oxide.
(a) Identify
the element.
(b) Write
the electronic configuration.
(c) Write a
balanced equation when it burns in the presence of air.
(d) Write a
balanced equation when this oxide is dissolved in water
(e) Draw the
electron dot structure for the formation of this oxide.
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question_answer118)
An element X
(atomic number 17) reacts with an element Y (atomic number 20) to form a
divalent halide.
(a) Where in
the periodic table are elements X and Y placed?
(b) Classify
X and Y as metal (s), non-metal (s) or metalloid (s).
(c) What
will be the nature of oxide of element Y? Identify the nature of bonding in the
compound formed.
(d) Draw the
electron dot structure of the divalent halide.
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question_answer119)
Atomic
number of a few elements are given below 10, 20, 7, 14
(a) Identify
the elements.
(b) Identify
the group number of these elements in the periodic table.
(c) Identify
the periods of these elements in the periodic table.
(d) What
would be the electronic configuration for each of these elements?
(e) Determine
the valency of these elements.
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question_answer120)
Complete the following
crossword puzzle (Figure).
Across
(1) An
element with atomic number 12.
(2) Metal
used in making cans and member of group 14.
(3) A
lustrous non-metal which has 7 electrons in its outermost shell.
Down
(2) Highly
reactive and soft metal which imparts yellow colour when subjected to flame and
is kept in kerosene.
(5) The
first element of second period.
(6) An
element which is used in making flurescent bulbs and is second member of group
18 in the modern periodic table.
(7) A
radioactive element which is the last member of halogen family.
(8) Metal
which is an important constituent of steel and forms rust when exposed to moist
air.
(9) The first
metalloid in modern periodic table whose fibres are used in making bullet-proof
vests.
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question_answer121)
(a) In this ladder
(Figure) symbols of elements are jumbled up. Rearrange these symbols of
elements in the increasing order of their atomic numbers in the periodic table.
(b) Arrange them in
the order of their group also.
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question_answer122)
Mendeleev predicted
the existence of certain elements not known at that time and named two or them
as Eka-silicon and Eka-aluminium.
(a) Name the
elements which have taken the place of these elements.
(b) Mention
the group and the period of these electron in the modern periodic table.
(c) Classify
these elements as metals, nonmetals or metalloids.
(d) How many
valence electrons are present in each one of them?
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question_answer123)
.
(a)
Electropositive nature of the element (s) increases down the group and
decreases across the period.
(b)
Electronegativity of the element decreases down the group and increases across
the period.
(c) Atomic size
increases down the group and decreases across a period (left to right),
(d) Metallic
character increases down the group and decreases across a period.
On the basis
of' the above trends of the periodic table, answer the following about the
electron with atomic numbers 3 to 9.
(a) Name the
most electropositive element among them.
(b) Name the
most electropositive element.
(c) Name of
the element with smallest atomic size.
(d) Name me
element which is a metalloid.
(e) Name the
element which shows maximum valency.
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question_answer124)
An element X
which is a yellow solid at room temperature shows catenation arid allotropy. X
forms two oxides which are also formed during the thermal, decomposition of
ferrous sulphate crystals and are the major air pollutant
(a) Identify
the element X.
(b) Write the
electronic configuration of X.
(c) Write
the balanced chemical equation for the thermal decomposition of ferrous
sulphate crystals?
(d) What
would be the nature (acidic/basic) of oxides formed?
(e) Locate
the position of the element in the modern periodic table.
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question_answer125)
An element X
of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in
presence of the catalyst to form a compound, ammonia which has a characteristic
pungent smell.
(a) Identify
the element X. How many valence electrons does it have?
(b) Draw the
electron dot structure of the diatomic molecule of X. What type of bond is
formed in it?
(c) Draw the
electron dot structure for ammonia and what type of bond is formed in it?
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question_answer126)
Which group
of elements could be placed in mendeleev's periodic table without disturbing
the original order? Give reason.
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question_answer127)
Give an account of
the process adopted by Mendeleev for the classification of elements. How did he
arrive at "periodic law"?
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