Question

question 18 (1 point)
the atomic number and mass number for calcium 39 are 20 and 39, respectively.
how many electrons are in one atom?
1
19
20
39

Explanation:

Step1: Recall the concept of atomic structure

In a neutral atom, the number of electrons is equal to the atomic number. The atomic number represents the number of protons, and in a neutral atom, protons (positive charge) are balanced by electrons (negative charge).

Step2: Apply the concept to calcium - 39

Given that the atomic number of calcium - 39 is 20. So, for a neutral calcium atom, the number of electrons should be equal to the atomic number. So the number of electrons \(= 20\).

Answer:

20 (corresponding to the option with 20, e.g., if the option is C. 20, then the answer is C. 20)