ANSWER
see explanation
EXPLANATION
Determine the number of protons, number of neutrons in the nucleus:
He2 3
He2 4
Mg12 24
Na1123
Ti2248
the lower atomic number is the number of protons
the higher atomic number is neutrons + protons
so He-3 has 2 protons and (3-2=1) neutron
he-4 2 protons and (4-2 = 2) neutrons
Mg-24 has 12 protons and (24-12=12) neutrons
Na-23 has 11 protons and (023-11=12) neutrons
Ti-48 has 22 protons and (48-22=26) neutrons
