Question

An element have atomic weight $40$ and its electronic configuration is $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6}$. Then its atomic number and number of neutrons will be:

• A. 18 and 22
• B. 22 and 18
• C. 20 and 20
• D. 40 and 18

Answer 1

Answer: (A)

18 and 22

Answer 2

Given, electronic configuration $=1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6}$ and atomic weight $=40$ Hence, atomic number $=2+2+6+2+6$ $=18$ Number of neutrons $=$ atomic weight $-$ atomic number $=40-18=22$