Question

21 multiple choice 4 points
an atom has 20 protons and 20 electrons. how many neutrons does calcium - 40 have?
40
20
0
10

Explanation:

Step1: Recall atomic mass formula

Atomic mass = Protons + Neutrons.

Step2: Identify given values

Calcium - 40 has an atomic mass of 40 and 20 protons.

Step3: Calculate neutrons

Neutrons = Atomic mass - Protons = 40 - 20.

Answer:

20 (The second option in the multiple - choice list)