Bonding – Learning Outcomes State what a molecule is. Recall that ionic bonding is an attraction between positive and negative ions. HL: Describe ionic bonding using NaCl and MgO as examples. Understand that covalent bonds involve the sharing of pairs of electrons. HL: Describe the bonding in H2, O2, H2O, CH4 as examples of covalent bonding. HL: Investigate the ability of ionic and covalent substances to conduct electricity.

Define Ionic Bonding All atoms “want” to have a full outer electron shell. First shell is full with 2 electrons. Second and third shells are full with 8 electrons. Atomic bonding is when atoms lose, gain, or share electrons to gain a full outer electron shell. The combination of two or more atoms bonded together is called a molecule. It is the smallest particle of an element or compound that can exist on its own.

Define Ionic Bonding Atoms on their own are usually neutral – they have the same number of positive protons and negative electrons. If an atom loses electrons, it has more positive protons than negative electrons, becoming a positive ion. If an atom gains electrons, it has more negative electrons than positive protons, becoming a negative ion.

Define Ionic Bonding An ionic bond is formed from the force of attraction between two oppositely charged ions. Consider sodium [2, 8, 1] and chlorine [2, 8, 7]

Describe Ionic Bonding Sodium can give up one electron to gain a full outer shell. Chlorine will get a full outer shell if it gains one electron.

Describe Ionic Bonding If sodium gives its outer electron to chlorine, they will both have full shells.

Describe Ionic Bonding This will make sodium positively charged and chlorine negatively charged.

Describe Ionic Bonding The positive and negative ions are attracted to each other and form an ionic bond, creating sodium chloride, NaCl.

Describe Ionic Bonding Describe the ionic bond between magnesium and oxygen: Write out the electron configuration for each atom. Think about how to give each atom a full outer shell. Draw out the final ions that are bonded together.

Understand Covalent Bonds In ionic bonds, atoms gain or lose electrons. Atoms want to have full outer shells, but they also don’t like to give up electrons. In some cases, electrons are shared between atoms.

Describe the Bonding in H2 A pair of hydrogens can’t agree on which should give up an electron, so they share theirs.

Describe the Bonding in CH4 Carbons [2, 4] have 4 electrons in their outer shell, so can form up to four bonds. Hydrogen [1] can only form one bond as it only has one outer electron.

Describe the Bonding in CH4 Thus, one carbon bonds with four hydrogens.

Describe Covalent Bonding Draw the covalent bond formed in oxygen gas (O2) and water (H2O). Write out the electron configuration for each atom. Think about how to give each atom a full outer shell. Draw out the final molecules that are bonded together.

Investigate Conduction in Ionic and Covalent Substances Prepare a sample of salt water and a sample of tap water in separate beakers. Connect a light bulb in series with a power supply and the beaker of salt water. Note that the bulb lights with sufficient voltage. Replace the beaker of salt water with the beaker of tap water. Note that the bulb does not light.

Investigate Conduction in Ionic and Covalent Substances The bulb only lights when in the salt water solution. As salt water is ionic and tap water is covalent, this suggests that ionic substances conduct electricity, while covalent substances do not.