Question

Atom X contains seven protons and seven neutrons. atom Z contains seven protons and eight neutrons. which of the following statements correctly describes the two atoms?

A.they are isotopes.
B.they are radioactive.
C they have the same mass number.
D they are atoms of different elements.

Answer 1

The correct answer is option A: they are isotopes.

Step-by-step explanation:

From atom X we know that the number of protons is 7 and the number of neutrons is 7 and from atom Z we know that the number of protons is 7 and the number of neutrons is 8.

Since the number of protons of atom X and atom Z is the same, we have that atom X and atom Z is the same element. The difference in the number of neutrons tells us that atom X and atom Z are isotopes. Remember that an isotope is one element that has atoms with different numbers of neutrons.

The mass number is given by:

`A = p + n`

Where n is the number of neutrons and p is the number of protons.

For atom X and atom Z we have:

`A_(x) = 7 + 7 = 14`

`A_(z) = 7 + 8 = 15`

Hence, they have a different mass number.

We know that the element with 7 protons is nitrogen. The first isotope is
`^(14)_(7)N` and the second isotope is
`^(15)_(7)N`. Both isotopes are stables (they are not radioactive).

Therefore, the correct answer is option A: they are isotopes.

I hope it helps you!