Question

what is the atomic number of mg²⁺? a 12 b 24 c 25 d 55 question 28 what is the atomic number of na⁺? a 11 b 16 c 23 d 32 last saved 9:59:06 pm

Explanation:

First Question (Atomic number of $\boldsymbol{\ce{Mg^{2+}}}$)

The atomic number of an element is determined by the number of protons in its nucleus. Ions (like $\ce{Mg^{2+}}$) are formed by gaining or losing electrons, but the number of protons (and thus the atomic number) remains the same as the neutral atom. Magnesium (Mg) has an atomic number of 12, so $\ce{Mg^{2+}}$ also has an atomic number of 12.

The atomic number is based on the number of protons. $\ce{Na^{+}}$ is a sodium ion, formed by losing an electron from neutral sodium (Na). The atomic number of sodium is 11, so $\ce{Na^{+}}$ still has an atomic number of 11 (since only electrons are lost, protons remain unchanged).

Answer:

A. 12

Second Question (Atomic number of $\boldsymbol{\ce{Na^{+}}}$)