Question

An element with the atomic number $19$ will most likely combine chemically with the element whose atomic number is :

• A. $17$
• B. $11$
• C. $18$
• D. $20$

Answer 1

Answer: (A)

$17$

The element with atomic number 19 will have the electronic configuration $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^1$. So, it has 1 valence electron. The element with atomic number 17 will have the electronic configuration $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$. This element with atomic number 17 needs 1 electron to complete its octet whereas element with atomic number 19 has an extra electron. Hence, an element with atomic number 19 is most likely to combine with the element with atomic number 17.