Question

(a) What are valence electrons? Where are valence electrons situated in an atom ?
(b) What is the number of valence electrons in the atoms of an element having atomic number 13 ? Name the valence shell of this atom.

Answer 1

(a) In an atom, the electrons are arranged in different shells. The electrons found in the outermost orbit of an atom are called valence electrons.
So, valence electrons are situated in the outermost orbit of an atom.

(b) The electronic configuration of the element with atomic number 13 is (2, 8, 3).  There are 3 valence electrons present in the outermost shell in the given element.
Valence shell of this atom is M.