Question

The electronic configuration of an element having atomic number $17$ is:

• A. $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$
• B. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}4s^1$
• C. $1s^{2}2s^{2}2p^{6}3s^{2}3p_x^{2}3p_z$
• D. $1s^{2}2s^{2}2p^{6}3s^{2}3p^{2}4s^{2}4p^1$

Answer 1

Answer: (A)

$1s^{2}2s^{2}2p^{6}3s^{2}3p^5$

If the atomic number is 17, there must be 17 protons and 17 electrons. Starting from the lowest level, we add electrons to each higher level until we have reached 17 electrons.

The electronic configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$