Electron capture occurs when one of the electrons in the atom is captured by the atom's nucleus. The captured electron combines with one proton to form a neutron.
We have to find the nuclide that is produced when the aluminum-28 undergoes an electron capture.
If we look for the atomic number of Al in the periodic table we will see that it is 13. That means that it has 13 protons. Then we are given the atomic mass of aluminum, it is 28. That means that if we add the number of protons and the number of neutrons we get 28.
atomic mass = n° of protons + n° of neutrons = 13 + 15 = 28
atomic number = n° of protons = 13
The nucleus of the aluminum atom will capture one electron that will combine with a proton of the nucleus to form a neutron. So the atomic number will change because it will have 1 proton less. But the atomic mass won't change because we are losing one proton but winning a neutron, so it remains the same. After the electron capture, the new nuclide will have:
atomic mass nuclide = n° of protons + n° of neutrons = 12 + 16 = 28
atomic number nuclide = n° of protons = 12
If we look for the element that has an atomic number of 12 in the periodic table we will see that it is magnesium.
Finally we can express this like a reaction:
28 0 28
Al + e --------> Mg
13 -1 12
Answer:
28
Mg
12
