Question

proton = 6, neutron = 2,
electron = 6
proton = 8, neutron = 8,
electron = 10
proton = 16, neutron = 8,
electron = 10
proton = 8, neutron = 16,
electron = 8
how many protons, neutrons, and electrons?

Explanation:

Step1: Determine the number of protons

The atomic number (the number in the upper - left corner of the element symbol in the periodic table) represents the number of protons. For oxygen ($O$), the atomic number is $8$, so the number of protons $= 8$.

Step2: Determine the number of neutrons

The mass number (the number in the upper - right corner of the element symbol, ignoring the charge for mass - number calculation) is $16$. The formula for the mass number $A$ is $A=\text{number of protons}(p)+\text{number of neutrons}(n)$. We know $p = 8$ and $A=16$. Then $n=A - p$. Substituting the values, we get $n=16 - 8=8$.

Step3: Determine the number of electrons

The charge of the ion is $- 2$. For a neutral atom, the number of electrons ($e$) is equal to the number of protons. But for an ion with charge $q$, the formula is $q=p - e$. We know $p = 8$ and $q=-2$. Then $-2=8 - e$, and solving for $e$ gives $e=8 + 2=10$.

Answer:

Protons: $8$, Neutrons: $8$, Electrons: $10$ (corresponding to the blue box: proton = 8, neutron = 8, electron = 10)