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

Answer:

The correct answer is option A: they are isotopes.

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!