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

The atomic number of an element corresponds to the number of protons it has. In this case, the atomic number is 12, which means the element has 12 protons.

The mass number is the sum of the number of protons and neutrons in an atom. The mass number is given as 40. So, we can set up the equation:

\[ \text{Mass number} = \text{Number of protons} + \text{Number of neutrons} \]

Substituting the known values:

\[ 40 = 12 \text{ (protons)} + \text{Number of neutrons} \]

To find the number of neutrons, we can rearrange the equation:

\[ \text{Number of neutrons} = 40 - 12 = 28 \]

Therefore, the element has 12 protons and 28 neutrons.

So, the correct answer is C) The element has 12 protons and has 28 neutrons.