To determine the identity of the atom that results from the decay of a radioactive magnesium (Mg) atom by emitting a positron, we need to understand the process of positron emission. Here are the detailed steps:
1. Identify the Initial Atom: The initial atom is magnesium (Mg), which has an atomic number of 12. This means magnesium has 12 protons in its nucleus.
2. Understand Positron Emission: In the process of positron emission, a proton in the nucleus is converted into a neutron, and a positron (which is the antimatter counterpart of an electron) is emitted. This process decreases the atomic number by 1 because the number of protons (which determine the atomic number) is reduced by one.
3. Calculate the Resulting Atom's Atomic Number:
- Original atomic number of Mg: 12
- Positron decay decreases this number by 1.
- Resulting atomic number = 12 - 1 = 11
4. Identify the Element with Atomic Number 11:
- The periodic table tells us that the element with atomic number 11 is sodium (Na).
Therefore, after the positron emission, the identity of the resulting atom is sodium (Na).
Thus, the correct answer is:
D. sodium (Na)
