Ionic Bonds

Essential Question: How do ionic bonds form?

What is an Ion

• An ion is any atom or combination of atoms that has a charge, negative or positive.

• An ion is formed when electrons are add or taken away from an atom.

• They are never formed by protons being added or removed, NEVER.

• Opposite charges of atoms attract each other.

Why do Ions form?

• Ions form because atoms want to have a complete octet.

• An Octet is 8 electrons in the outer energy level or shell.

• How can we make complete shells?

How Ionic Bonds Form?

• An ionic bond is the force of attraction that holds together positive and negative ions.

• It forms when atoms of a metallic element give up electrons to atoms of a nonmetallic element.

Ions

• When an atom loses a negative electron, the overall charge becomes positive

• It’s called a cation• When an atom gains an

electron, the overall charge becomes negative

• It’s called an anion

Table Salt

• Sodium and Chlorine have equal and opposite charges.

• They “attract” and cling together in a strong ionic bond.

• Ionic bonds form between metal and nonmetal atoms

Why Ionic Bonds Form

• Ionic bonds form only between metals and nonmetals. That’s because metals “want” to give up electrons, and nonmetals “want” to gain electrons.

• Look at the Lewis Dots that you drew on your Periodic Table & think about the Octet Rule

• Alkali Metals (#1) bond with Halogens (#17)• Predict which might bond with Alkaline Earth Metals• Alkaline Earth Metals (#2) bond with the Oxygen

Family (#16)

Energy and Ionic Bonds

• Energy holds the electrons in orbit around the nucleus

• Energy is needed to remove valence electrons from one atom and attach them to another

• These ionic bonds are very strong and difficult to break – for example, try burning salt

• These compounds have high melting and boiling points and are good electrical conductors.

• Because water has polar bonds, ionic compounds do dissolve in water.

Ionic Bonds form Crystals

• Many compounds form molecules, but ionic compounds form crystals instead.

• A crystal consists of many alternating positive and negative ions bonded together in a matrix.

Ionic Crystals

• In this demo, we will cause a minor chemical reaction of several metals and nonmetals:

• We’ll use table salt, which contains Sodium and Chlorine

• “Bluing” which contains Ferric hexacyanoferrate which has Iron, Nitrogen, Carbon, and Oxygen

• Water = Oxygen and Hydrogen

Ionic Crystals Demo

• In a glass or plastic bowl, put some pieces of charcoal, porous brick, tile, cement or sponge.

Day 1: Over the base material, 10 ml of water, 10 g salt and 10 ml Mrs. Stewart's Bluing.Day 2: Add two more tablespoons of salt.Day 3: Pour into the bottom of the bowl (not directly on the base material) two tablespoons each of salt, water, and Mrs. Stewart's Bluing, and then add a few, vegetable coloring each piece.

Observe over the next few days…

• Next week, we’ll discuss covalent bonds and create a polymer.

• You will be asked to compare and contrast the result of these two activities.