Question

Sally is making a model of a magnesium atom with an atomic mass number of 24 for her chemistry class. She has foam balls for the protons, neutrons, and electrons. She has added 6 neutrons to her model so far. How many more neutrons does she need to add to complete her neutral atom of magnesium?

Answer 1

The answer is; 6

The atomic number of magnesium (the number of protons ) is 12. Since the mass number is the number of protons + neutrons. The neutron number can be derived as 24 -12 = 12.

Since she already has 6 neutrons, she needs to add (12 – 6) more neutrons = 6

Answer 2

Answer: She needs to add 8 more neutrons to her model.

Explanation:

Magnesium is an element which has an atomic number of 12.

Atomic number is defined as the umber of electrons or protons present in that atom.

Atomic number = number of electrons = Number of protons = 12

Atomic mass is defined as the sum of number of protons and neutrons that are present in an atom.

Atomic mass = Number of protons + Number of neutrons

We are given the atomic mass of magnesium which is 24

So, Number of neutrons in this element = 24 - 12 = 12

For a model, she has added 6 neutrons and total number of neutrons that must be added in the model are 12.

So, she is short of (12 - 6) = 8 neutrons.

Hence, she needs to add 8 more neutrons to her model.