Question

A, B, C are three elements with atomic numbers, Z-1, Z, and Z+1 respectively. B is an inert gas.

Identify the elements having same valence shell.

• A. A, B
• B. B, C
• C. A, C
• D. A, B, C

Answer 1

The correct option is A A, B

Three elements A,B and C. B is a noble gas, A has atomic number 1 less than B and C has 1 more than B. Hence number of valence shell is same in A and B because on adding one electron to Noble gas that is 18 group next electron will occupy, alkali metals group in a next period hence increases in shell number.