Answer:
2. Oxidation number
Explanation:
In an atom, M, nuclide notation is expressed as:
ₓᵃMⁿ
Where a is mass number (Protons + neutrons)
x is atomic number (Protons)
And n is the charge of the atom (Protons - Electrons ; Oxidation number)
The atom Cu²⁺ has lost 2 electrons, changing, thus, its oxidation number.
Right answer is:
