Question

the model below shows a calcium atom. how many electrons are in the third energy level? 2 8 18 20

Explanation:

Step1: Recall calcium's atomic number

Calcium has atomic number 20, so it has 20 electrons.

Step2: Know electron - shell filling rules

The first energy level can hold 2 electrons, the second can hold 8 electrons.

Step3: Calculate electrons in third level

20 - (2 + 8)=10. But in a simple Bohr - like model for calcium's electron configuration, the third energy level is filled with 8 electrons before the fourth starts to fill.

Answer:

8