Question

question 1. which of the following statements are true about an atom with atomic number 15 and mass number 31? (select all that apply.) it has 15 protons. it has 31 neutrons. it has 15 electrons if it is neutral. it has 16 neutrons.

Explanation:

Step1: Recall atomic number concept

The atomic number is equal to the number of protons. Given atomic number = 15, so number of protons = 15.

Step2: Recall electron - proton relationship in neutral atoms

In a neutral atom, the number of electrons is equal to the number of protons. Since number of protons = 15, number of electrons = 15 if it is neutral.

Step3: Recall mass - number formula

Mass number = number of protons+number of neutrons. Given mass number = 31 and number of protons = 15. So number of neutrons=mass number - number of protons = 31 - 15=16.

Answer:

It has 15 protons.
It has 15 electrons if it is neutral.
It has 16 neutrons.