Answer:
12, 28, 16
Explanation:
If we are trying to find mass, neutrons are our guy. 28 "mass points" means 28 neutrons. Each neutron is one point
We know there are 12 protons and electrons if we look at a table of elements, the number in the top-left is always the number of protons and we can subtract mass from the protons to get our electrons
1. 2 H2 + O2 = 2 H2O
2. 6 K + B2O3 = 3 K2O + 2 B
3. 10 Na + 2 NaNO3 = 6 Na2O + N2
