Question

The group number, number of valence electrons and valency of an element with atomic number $15$, respectively, are:

• A. $16,5\text{and}2$
• B. $15,5\text{and}3$
• C. $16,6\text{and}3$
• D. $15,6\text{and}2$

Answer 1

The correct option is B $15,5\text{and}3$

The group number, number of valence electrons and valency of an element with atomic number 15 are 15, 5 and 3 respectively. Modern periodic table is based on the atomic number. Number of valence electrons present in an atom decides the group number. Electronic configuration of element having atomic number$15=1s^{2}2s^{2}2p^{6}3s^{2}3p^3$.
Valence electrons =$3s^{2}3p^3=5\text{valence electrons}$
As five electrons are present in valence shell, its group number is $15$. Valency of element having atomic number $15$ can be either $5$ or $3$.