Section 1-3Ionic Bonds

Habit Of The Mind#2 I teach my students to

manage impulses and delay gratification to attain long term goals.

ObjectivesL.1.3.1. Describe ions and explain

how they form.

L.1.3.2. Explain how the formulas and names of ionic compounds are written.

L.1.3.3. Identify properties of ionic compounds.

How Ions FormAtoms with 5-6-7 valence electrons will

usually accept enough electrons to increase that number to 8 and become stable.

Atoms with 1-2-3 valence electrons will usually give up enough to lose their outer shell and be left with a full valence set of electrons.

These two types of atoms will become electrically charged and are then called IONS.

How Ions FormWhen an atom loses an

electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Objective L.1.3.1

How Do We Know If An Atom Will Gain or Lose?

The answer is in the number of valence electrons. The atom will do whatever requires less energy.

Look at the following slide to decide what requires the least amount of energy. The obvious choice is the correct choice.

How Ions Form

Polyatomic IonsWhat does POLY mean?

It means many.

What does atomic mean?

It means atom.

What does Polyatomic mean?

It means many atoms.

A polyatomic ion is just a group of atoms (a molecule) that behave like a single ion.

Polyatomic Ions

Ionic BondsAn ionic bond is the attraction between two

oppositely charged ions.

Ionic bonds form as the result of attraction between a positively charged ion and a negatively charged ion. Obj. L.1.3.1

A compound formed between a positive and negative ion is called an Ionic Compound.

Ionic compounds form between a metal and a nonmetal.

Chemical Formulas And Names

Compounds are represented by a chemical formula.

What two pieces of information does a chemical formula give you?

It tells you which elements are in that compound by giving you the chemical symbol for each element and,

It tell you how many of each element are part of that compound.

Formulas Of Ionic CompoundsWhen ionic compounds form, the ions bond in

such a way as to balance the charges. The chemical formula of the compound reflects this. L.1.3.2.

A chlorine atom only needs to gain 1 electron to fill it’s valence shell so the chloride ion will have a charge of -1.

A magnesium ion wants to lose 2 electrons to shed it’s outer shell so the magnesium ion will have a charge of +2.

These charges need to balance.

Formulas Of Ionic Compounds

Formulas Of Ionic CompoundsSo, if magnesium wants to give away 2 electrons

but chlorine will only take 1, what do we need to take the other electron from magnesium?

Another chlorine atom.

So 1 magnesium atom will bond with 2 chlorine atoms. What is the resulting chemical formula?

MgCl2

This is called Magnesium Chloride and is a form of salt.

Naming Ionic CompoundsFor an ionic compound, the name of the

positive ion comes first and is followed by the name of the negative ion. L.1.3.2.

Ionic bonds most often occur between a metal and a nonmetal. The metal becomes the positive ion because it gives up electrons and the nonmetal becomes the negative ion because it receives electrons.

If the negative ion is an element, the ending changes to –ide. Example: Magnesium Chloride.

Properties Of Ionic Compounds

In general, ionic compounds are hard, brittle crystals and they have high melting points. When dissolved in solution, the ions make good conductors of electricity. L.1.3.3.

Ionic Crystals Pg. 26

High Melting Points

Electrical Conductivity

Storing Heat In Salt

Storing Heat In Salt