Chapter 4, Problem 70A

If an atom has 18 electrons, how many protons does it have?

Interpretation Introduction

Interpretation:

Protons of an atom with 18 electrons is to be calculated.

Concept introduction:

The number of protons in an atom can also be mentioned as Atomic number of an element.

Answer to Problem 70A

Number of protons in an atom with 18 electrons is 18.

Explanation of Solution

The number of protons in an atom is equal to its atomic number. All atoms are neutral; therefore numbers of protons and electrons in an atom must be equal.

$\text{Atomic number = number of protons = number of electrons}$

$\text{Number of electrons in given atom = 18}$

Therefore, number of protons in an atom will be 18.

Conclusion

Number of electrons in an atom must be equal to number of protons. So, an atom with 18 electrons will also have 18 protons.