Question

1. magnesiums atomic number is 12 and its mass number is 24. magnesium has 12 protons, 12 electrons, and 12 neutrons.
2. what determines the chemical properties of an element?

atomic number
number of electron shells
number of valence electrons
physical state at room temperature

Explanation:

The chemical properties of an element are mainly determined by the number of valence electrons. Valence electrons are involved in chemical bonding and reactions. The atomic number determines the element's identity. The number of electron shells affects the element's size and some properties but is not the main determinant of chemical properties. The physical state at room temperature is a physical property, not a chemical one.

Answer:

C. number of valence electrons