question_answer

  (a) Boron atom has atomic mass of 11u and has 5 protons in its nucleus. How many neutrons does it have? (b) What are the number of valence electrons in this atom, and its ion?

Answer:

                           (a) Mass number of boron is equal to its atomic  mass but has no unit.                          Mass number (A) of boron =11                 Number of protons in the nucleus = 5           Atomic number of the element (Z) = 5           Number of neutrons =A- Z= 11 -5 = 6 (b) Electronic configuration of B = 2,3.          No. of valence electron in B = 3.         It loses three electrons to form B + ion. Thus, the configuration of B3+ = 2. Number of valence electrons in B + = 2.