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Ions

What do tasting a pinch of salt, touching a metal spoon, and turning on the light have in common? They all involve ions. Ions are tiny charged particles that help make all of these possible. Chemically, they explain why some compounds conduct electricity and why some substances dissolve in water. Knowing about ions is like knowing the secret code of the universe.

What is an Ion?

An ion is a charged atom or a collection of atoms. The charge imbalance is a result of the number of electrons being unequal to the number of protons.

• An atom with the same number of protons and electrons is said to be neutral.
• An atom that loses electrons becomes positively charged.
• An atom that gains electrons becomes negatively charged.

Key idea in simple words:

• Charge is loss or gain of electrons in an atom.
• The nucleus contains protons that don't move. However, when an atom gets ionized, the only subatomic particles that move are the electrons.

Why are ions created?

To become chemically stable. Stability occurs when there is a complete outer shell. With a partial outer shell some atoms become reactive, while completely filled outer shell atoms become unreactive.

Atoms are trying to mimic the outer electron shell arrangement of noble gas atoms.

What makes noble gas atoms so unique is that they have a complete outer shell, and so they don't chemically react with others.

To become stable, atoms must either gain or lose electrons.

To create ions, atoms must use energy.

Classification of Ions

Ions can be classified into two categories based on charge.

Valence Electrons and Ion Formation

Valence electrons are all electrons in the last shell of the atom. These electrons determine how the atom will respond.

• Atoms with 1, 2, or 3 valence electrons will likely lose electrons.
• Atoms with 5, 6, or 7 valence electrons will likely gain electrons.
• Atoms with 8 valence electrons are already stable.

Pattern:

• Few outer electrons → lose electrons → positive ion
• Almost full outer shell → gain electrons → negative ion

Electron Transfer and ionic bonding

When ions are created, electrons are transferred from one atom to another. This creates ionic bonding.

• One atom loses electrons and becomes a cation.
• The other atom gains those electrons becoming an anion.
• Opposite charges attract each other.
• This attraction keeps the ions in a compound together.

This attraction is known as the electrostatic force. This is what keeps ionic compounds together as solid crystals.

Formation of Ionic Compounds

An ionic compound is created when positive ions and negative ions combine in a fixed ratio so the all the overall charge becomes zero.

Important points:

• The compound must be electrically neutral.
• The charges of ions balance each other.
• The formula shows the simplest ratio of ions.

Take, for example, one Na⁺ and one Cl⁻. These two ions combine to form a neutral compound.

Another example is two Na⁺ ions combining with one O²⁻ ion.

This is the basic charge balancing rule for constructing chemical formulas.

Constructing the Chemical Formulas of Ionic Compounds

Chemical formulas are a representation of the ratio of the different ions in an ionic compound. The objective is to have the total positive charge equal the total negative charge.

The total charge is neutral.

Basic principles:

• The positive ion is written first.
• The negative ion is written second.
• The charges should be balanced to make the compound neutral.

Things to remember:

• The charge of the ions determines the total number of each ion needed.
• The final formula will use subscripts to show the total number of ions of that type.
• The formula will show the simplest whole number ratio of ions.

Polyatomic Ions

Ions that are formed from more than one atom that are bonded together are known as polyatomic ions.

Important aspects:

• While the ions are formed from multiple atoms, they will act as a single unit with a single overall charge.
• The individual atoms inside the ion are held together by covalent bonds.
• The entire group of atoms carries either a positive or negative charge.

During chemical reactions, polyatomic ions behave as though they are single charged ions.

Properties of Ionic Compounds

A number of unique chemical and physical properties are found in ionic compounds due to the presence of strong forces of attraction that hold the individual ions together.

Typical Properties include:

• High melting and boiling points - Strong electrostatic forces hold ions tightly in a lattice.
• Crystalline solid structure - Ions arrange in a repeating pattern called a crystal lattice.
• Solubility in water - Many ionic compounds dissolve because water stabilizes ions.
• Electrical conductivity - Solid ionic compounds do not conduct electricity.
• Molten or dissolved ionic compounds conduct electricity because ions can move.

These properties help identify ionic substances in the lab and in daily life.

Ions in Solutions and Electrolytes

When an ionic compound dissolves in water, it breaks into free ions. This process is called dissociation.

The solution now contains moving charged particles.

Such a solution is called an electrolyte.

Electrolytes can conduct electricity.

Everyday examples can include:

• Salt solution conducts electricity.
• Sports drinks contain ions that help body functions.
• Batteries and cells depend on ion movement to produce current.

Naming ionic compounds

When naming ionic compounds there is a pattern. This pattern is universal to scientists anywhere around the globe.

Here are the basic ideas:

• Name the positive ion first.
• Then name the negative ion.
• For simple anions, the ending often changes to "-ide".

For example,

• Sodium + chloride becomes sodium chloride.
• Calcium + fluoride becomes calcium fluoride.

For polyatomic ions:

• The group name stays the same.
• Compound Names Show Which Ions are Present

Ions and Their Function in Chemical Reactions

Ions are important in many chemical reactions, particularly in solutions.

Here are some of the important things to think about:

• Ions can join together to make new substances.
• Ions must be present in reactions and be able to move around so they can create new substances.
• In some reactions, the ions come together to make an insoluble solid, (which is called a precipitate).

Because of these reasons, you can think of ions like the active agents that trigger reactions that occur in water.

Everyday Examples of Ions

Your everyday life is strongly influenced by ions.

Ions are present in everyday life, strongly influencing technology, biology, and chemistry.

Why It is Important to Learn About Ions

Ions are the basis of important advanced topics in chemistry and science. The understanding of ions explains how compounds are formed and links the atomic structure and chemical bonding.

Also, it helps to understand reactions, solutions, electricity, and connects real life and learning.

Understanding ions allows you to appreciate chemistry as more than abstract symbols. You begin to see it as a dynamic system composed of charged particles that construct the physical world around you.