Calcium has an atomic number of 20. An atom of calcium has ____ electrons in its first energy level and ____ electrons in its second energy level.
A)two; eight
B)four; four
C)six; six
D)eight; two
E)two; ten

Question

Quizplus · Accepted Answer

The first energy level can hold a maximum of 2 electrons, so calcium's first energy level would be filled with 2 electrons. The remaining 18 electrons would be in the second energy level, which can hold up to 8 electrons. Therefore, calcium would have 2 electrons in its first energy level and 8 electrons in its second energy level, making answer A the correct choice.

Calcium Has an Atomic Number of 20