Ions and Ionic Compounds

Formation of Ions by Electron Loss or Gain

Ions are electrically charged particles formed when atoms gain or lose electrons. The formation of ions occurs through two main processes:

Think of a game where players have different colored marbles. Each player wants to have a complete set of marbles of a specific color. However, some players are missing a few marbles. To complete their sets, they decide to trade their extra marbles with other players who are missing those marbles. In this scenario:

Sodium (Na) is like a player with an extra red marble (valence electron) in their set. They decide to give away the red marble, leaving them with a complete set. So, Na loses the red marble (electron) and becomes a sodium ion (Na+).

Magnesium (Mg) is like a player with two extra blue marbles (valence electrons). They give away both blue marbles, completing their set. Thus, Mg loses the two blue marbles (electrons) and becomes a magnesium ion (Mg2+).

Electron Loss (Cation Formation)

When an atom loses one or more electrons, it becomes positively charged and forms a cation. The number of protons surpasses the number of electrons, thereby creating a net positive charge. This process typically occurs for elements that have fewer electrons in their outermost shell than a stable noble gas configuration. By losing electrons, these atoms achieve a stable electronic configuration similar to the nearest noble gas. This cation formation through electron loss is typical for metallic elements on the left side of the periodic table, which have 1-3 electrons in their outermost shells.

For instance, sodium (Na) naturally has 11 electrons, with 1 electron in its outermost shell. Now sodium can either gain 7 electrons to have a complete outermost shell like Argon (18) or lose 1 electron to become stable noble gas is neon (Ne), which has 10 electrons and a full outer shell. It is therefore much easier for sodium to lose one electron than gain 7 electrons . If sodium loses an electron, it now has 10 electrons like neon, achieving a stable configuration by becoming Na+.

For example:

Sodium (Na): Sodium has one valence electron in its outermost shell. By losing this electron, it forms a sodium ion (Na+).

Magnesium (Mg): Magnesium has two valence electrons. By losing both electrons, it forms a magnesium ion (Mg2+).

Electron Gain (Anion Formation)

When an atom gains one or more electrons, it becomes negatively charged and forms an anion. This process typically occurs for elements that are close to achieving a stable noble gas configuration by gaining electrons. By gaining electrons, these atoms fill their outermost shell and attain a stable electronic configuration.

For instance, Chlorine (Cl) naturally has 17 electrons, with 7 electrons in its outermost shell. Now Chlorine can either gain 1 electrons to have a complete outermost shell like Argon (18) or lose 7 electrons to become stable noble gas is neon (Ne), which has 10 electrons and a full outer shell. It is therefore much easier for chlorine to gain one electron than lose 7 electrons . If chlorine gains an electron, it now has 10 electrons like neon, achieving a stable configuration by becoming Cl-.

Imagine a group of friends playing a game of catch with balls. Each friend has a goal of having a specific number of balls to feel satisfied. However, some friends are missing a few balls. To fulfill their goals, they ask their friends for some extra balls. In this analogy:

Chlorine (Cl) is like a friend who is missing one ball to complete their desired set. They ask another friend for an extra ball and receive it. Now, Cl has one additional ball (electron), making it a chloride ion (Cl-).

Oxygen (O) is like a friend who is missing two balls to complete their desired set. They ask two different friends for extra balls and receive them. Now, O has two additional balls (electrons), transforming it into an oxide ion (O2-).