Ions

When an Atom Is No Longer Neutral

A neutral atom has the same number of protons and electrons. An ion forms when an atom or group of atoms has an overall charge. Here, we focus first on ions made from one atom.

The Atomic Structure and Symbolism section from OpenStax explains that ions form when the number of electrons is not equal to the number of protons. The source can be opened through OpenStax's Atomic Structure and Symbolism.

Protons are in the nucleus and usually do not move during simple chemical processes. Electrons are the particles that change. So element identity stays locked by the number of protons, while ion charge is determined by the difference between protons and electrons.

A simple way to read charge is by its sign. Protons add positive count, while electrons add negative count. If the counts match, the result is $0$ or neutral. If electrons decrease, positive charge remains. If electrons increase, negative charge remains.

When an Atom Is No Longer Neutral

A neutral atom has the same number of protons and electrons. An ion forms when an atom or group of atoms has an overall charge. Here, we focus first on ions made from one atom.

The Atomic Structure and Symbolism section from OpenStax explains that ions form when the number of electrons is not equal to the number of protons. The source can be opened through

OpenStax's Atomic Structure and Symbolism.

A simple way to read charge is by its sign. Protons add positive count, while electrons add negative count. If the counts match, the result is

0

or neutral. If electrons decrease, positive charge remains. If electrons increase, negative charge remains.

Part to read	When an ion forms	Effect
Protons	Stay the same	The element does not change.
Neutrons	Stay the same for the same ion	The mass number does not change.
Electrons	Change	The ion charge changes.

Symbol	Atomic number	Mass number	Charge	Protons	Electrons	Neutrons
${}^{7}_{3}\mathrm{Li}$	$3$	$7$	$0$	$3$	$3$	$4$
${}^{7}_{3}\mathrm{Li}^{+}$	$3$	$7$
${}^{16}_{8}\mathrm{O}$	$8$	$16$
${}^{16}_{8}\mathrm{O}^{2-}$	$8$	$16$
${}^{27}_{13}\mathrm{Al}$	$13$	$27$
${}^{27}_{13}\mathrm{Al}^{3+}$	$13$	$27$

Ions

When an Atom Is No Longer Neutral

Ions

When an Atom Is No Longer Neutral

Charge Comes from the Difference

What Changes and What Stays

Worked Table for Ion Counts

Checking the Lithium Row