Question

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? 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

In the periodic table, the atomic number indicates the number of protons in the nucleus of an atom. The mass number 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. The mass number is 40, which is the sum of protons and neutrons.

To find the number of neutrons, you can use the formula:

\[ \text{Neutrons} = \text{Mass number} - \text{Atomic number} \]

So,

\[ \text{Neutrons} = 40 - 12 = 28 \]

Thus, the element has 12 protons and 28 neutrons.

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