A student looks up an element on the periodic table. The table says that the atomic number of the element is 12 and the mass number of the element is 40. What information do these two numbers convey about the element?

Question

A) The element has 40 protons and 12 neutrons
B) The element has 12 protons and 12 neutrons
C) The element has 12 protons and has 28 neutrons
D) The element has 28 protons and 40 neutrons

Answer 1

To understand the information conveyed by the atomic number and mass number:

• The atomic number (12) indicates the number of protons in the nucleus of the element.
• The mass number (40) is the total number of protons and neutrons in the nucleus.

Given that the atomic number is 12, this means the element has 12 protons. To find the number of neutrons, you can subtract the number of protons from the mass number:

Mass number = Number of protons + Number of neutrons 40 = 12 + Number of neutrons

Number of neutrons = 40 - 12 = 28

So, the element has 12 protons and 28 neutrons. Therefore, the correct answer is:

C) The element has 12 protons and has 28 neutrons.