An element with the electron configuration: [noble gas] ns2 (n - 1)d10 np3 has how many valence electrons. a. 2
b. 15
c. 3
d. 10
e. 5

The correct option is e. 5

Explanation:

An element with the electron configuration [noble gas] ns² (n - 1)d¹⁰ np³ belongs to the nitrogen group element - group 15 - in a period higher than 2. The element could be As, Sb or Bi. For example, arsenic (As) has the electron configuration [Ne] 4s² 3d¹⁰ 4p³.

The valence electrons are those in the highest energy level, in a s or p sublevel. For the elements with the general electron configuration [noble gas] ns² (n - 1)d¹⁰ np³ has 5 valence electrons: 2 electrons in a s sublevel and 3 electrons in a p sublevel. The electrons in the d orbital are in a lowest energy level (n-1).

Therefore, the correct option is e. 5.