Metalloids
Category : 10th Class
There are those elements which behave as metals as well as non-metals. They have four valence electrons.
e.g.
Carbon (C-6) : 2,4
Silicon (Si-14) : 2, 8, 4
Which one of the following is the poorest conductor of electricity?
(a) Copper
(b) Aluminium
(c) Lead
(d) Silver
(e) None of these
Answer: (c)
Sodium is a metal because:
(a) It is an element
(b) It has 11 electrons
(c) It has one valence electron
(d) It has 11 protons
(e) None of these
Answer: (c)
Explanation
It is one valence electron. So it can donate one electron and form cations.
Physical Properties of Metals
Physical properties of non-metals
Chemical Properties of Metals
Metals + Oxygen \[\to \] Metal oxides
Metal oxides are basic oxides and they react with acids to form salt and water
\[4Na+{{O}_{2}}\to 2N{{a}_{2}}O\]
\[N{{a}_{2}}O+{{H}_{2}}O\to 2NaOH\]
\[3Fe+2{{O}_{2}}\to F{{e}_{3}}{{O}_{4}}\]
Reactivity of metals with oxygen is : \[K>Na>Mg>Zn>Fe>Cu\]
Metal oxides, which are water soluble, are called alkali, e.g. \[N{{a}_{2}}O,\,\,{{K}_{2}}O\]
Metals + Water \[\to \] Metal oxide + Hydrogen gas
\[2Na+2{{H}_{2}}O\to 2NaOH+{{H}_{2}}\]
\[Mg+{{H}_{2}}O\to MgO+{{H}_{2}}\]
\[3Fe+4{{H}_{2}}O\to F{{e}_{3}}{{O}_{4}}+4{{H}_{2}}\]
Metals above hydrogen in reactivity series react with dilute acids to liberate hydrogen gas.
Metal + Acid \[\to \] Metal salt + Hydrogen gas
\[2Na+2HCl\to 2NaCl+{{H}_{2}}\]
\[Zn+{{H}_{2}}S{{O}_{4}}\to ZnS{{O}_{4}}+{{H}_{2}}\]
\[3Fe+8HN{{O}_{3}}\to 3Fe{{(N{{O}_{3}})}_{2}}+4{{H}_{2}}O+2NO\]
\[Mg+2HN{{O}_{3}}\to Mg\,{{(N{{O}_{3}})}_{2}}+{{H}_{2}}\]
(1 % Conc.)
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