Question

Which of the following elements shown as pairs with their atomic numbers belong to the same period?

• A. Z = 19 and Z = 38
• B. Z = 12 and Z = 17
• C. Z = 11 and Z = 21
• D. Z = 16 and Z = 35

Answer 1

Answer: (B)

Z = 12 and Z = 17

Answer 2

: $Z = 12,1s^{2}2s^{2}2p^{6}3s^{2}(n = 3)$

$Z = 17,1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}(n = 3)$