We both have 10 neutrons in our nuclei. what are we?

Fluorine and Neon have 10 neutrons in our nuclei

Explanation:

Each chemical element is characterized by the number of protons in its nucleus, which is called the atomic number Z. But in the nucleus of each element, it is also possible to find neutrons, the number of which can vary. The atomic mass (A) is obtained by adding the number of protons and neutrons in a given nucleus.

In an electronically neutral element the atomic number Z also indicates the number of electrons that rotates around the nucleus.

Being an isotope of an element that whose atomic number is the same, but the number of neutrons is different, then the atomic mass of an element is the weighted average mass of its natural isotopes. Therefore, the atomic mass of an element is not an integer.

Then

Mass number = Number of protons + Number of neutrons

→ Number of neutrons= Mass number - Number of protons

Then, obtaining the atomic mass and the atomic number in the periodic table, it is possible to calculate the number of neutrons in the following elements:

Atomic number = 9  

Mass number = 19

→ Number of neutrons = 19 - 9 = 10

Atomic number = 10

Mass number = 20

→ Number of neutrons = 20 - 10 = 10

Fluorine and Neon have 10 neutrons in our nuclei

i think it's letter a.