Structure of the atom

Isotopes have same atomic numbers and thus same number of electrons. Therefore, they have the same electronic configuration which provides them similar chemical properties.

Mass number = No. of protons + No. of neutrons = 31 ∴ Number of neutrons = 31 – Number of protons = 31 – 15 = 16

Figure number (ii) is correct because sodium ion (Na+ ) is formed when one electron is lost. Na  →    Na+  + le − (2,8,1)      (2,8) The valency…

(a) 0 (b) 1

Helium atom has 2 electrons in its valence shell and its duplet is complete. Hence, the valency is zero.

Helium has two electrons in its energy shell, while argon and neon have 8 electrons in their valence shells. As these have maximum number of electrons in their valence shells,…

The electrons present in the outermost shell of an atom or ion are known as valence electrons. In a chemical bond formation, only valence electrons of an atom take part.

The electronic distribution of Cl is 2, 8, 7. The L shell has eight electrons.

Atomic number of Al = Number of electrons = 13 Number of electrons in Al3+ = 13 - 3 = 10 Atomic number of chlorine = Number of electrons =…

Electronic configuration of P = 2, 8, 5 P atom gains 3e- to form P3- ∴ P3- has configuration = 2, 8, (5 + 3) = 2, 8, 8