Question

1. what is the atomic number of an atom that contains 40 protons, 40 electrons, and 51 neutrons?

□ 11
□ 40
□ 51
□ 91

Explanation:

Step1: Recall atomic number definition

Atomic number = number of protons

Step2: Match given proton count

Given protons = 40, so atomic number = 40

Answer:

$\boldsymbol{40}$ (Option: $\boldsymbol{\square}$ 40)