Hey there!
The atomic mass is the sum of the protons and electrons.
The charge of an atom is the difference between protons and electrons.
So, the number of protons is p, and p - 11 = -1.
Add 11 to each side and get p = 10. The atom has 10 protons.
The atom has 10 protons and 8 neutrons, the sum of the two is the atomic mass.
10 + 8 = 18
The atom has an atomic mass of 18.
Hope this helps!
The question is incomplete, the complete question is:
Write the net ionic equation for the below chemical reaction:
(c): 
<u>Answer:</u> The net ionic equation is 
<u>Explanation:</u>
Net ionic equation is defined as the equations in which spectator ions are not included.
Spectator ions are the ones that are present equally on the reactant and product sides. They do not participate in the reaction.
(c):
The balanced molecular equation is:

The complete ionic equation follows:

As ammonium and chloride ions are present on both sides of the reaction. Thus, they are considered spectator ions.
The net ionic equation follows:

Answer:
Turns into a neutron and a gamma ray and a positron are released.
Explanation:
3Ca(NO₃)₂(aq) + 2Na₃PO₄(aq) → Ca₃(PO₄)₂(s) + 6NaNO₃(aq)
3Ca²⁺ + 6NO₃⁻ + 6Na⁺ + 2PO₄³⁻ → Ca₃(PO₄)₂ + 6Na⁺ + 6NO₃⁻
3Ca²⁺ + 2PO₄³⁻ → Ca₃(PO₄)₂ (calcium phosphate is the precipitate)