What is the number of neutrons in an atom with atomic mass of 35, three energy levels, and 7 valence electrons?

Answer: the number of Neutron = 18

Explanation:

Mass number = 35

3 energy levels means 3 shells

1st shell = 2 electrons

2nd shell = 8 electrons

3rd shell = 7 electrons

Total = 17

Proton = 17

Neutron = Mass number - proton

Neutron = 35 - 17 = 18

The answer to your question is 18 neutrons

Explanation:

Data

Number of neutrons = ?

Atomic mass = 35

Three energy levels

seven valence electrons

Process

1. - We know that this element is on the third period (3 energy levels)

2. - We also know that this element is located on group 7A (it is a halogen)

3. - From the previous information, we conclude that this element is Chlorine.

4. - Chlorine has an atomic number of 17.

5. - The number of Neutrons = Atomic mass - atomic number

= 35 - 17

= 18