Chapter 7 Molecular compounds

The covalent bonds within these molecules are strong (covalent) but the bonds between molecules weak (intermolecular forces) and easy to break

• Usually gases or liquids at room temperature (if solid, they are soft solids) • Low melting points and boiling points • Do not conduct electricity

There are no Free electrons due to the strong electrostatic forces between the positive nuclei and the negative electrons keeping them in place.

Small molecules that join together by covalent bonds

Polymer due to the longer chains which contain more intermolecular forces Long chains get tangled meaning they will need more energy to be broken

A long chain molecule made from many monomers joining together.

Different structural forms of the same element are called allotropes

Molecules are atoms joined by covalent bonds

Both! Molecules can be compound ( such as water , H2O ) or element (Such as oxygen, O2)

Fullerenes have weak intermolecular forces between molecules and so have low melting point these weak forces also make the soft and slippery.

Fullerenes , Graphene , Graphite , Diamond

Simple

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Graphene has high melting point due to thew strong covalent bonds and can conduct electricity due to the delocalized electrons that carry electricity.

graphene is complex because it consists of a sheet of carbon atoms with no fixed formula

60 carbon atoms

Giant molecular structures have huge three-dimensional networks of carbon atoms linked by covalent bonds,

Graphite has a high melting point because of many strong covalent bonds that need a lot of energy to be broken. Graphite has three covalent bonds for each carbon atom. This gives graphite a layered structure and means that not all of its electrons are held in covalent bonds. This means it is a good electrical conductor due to the delocalized electrons. weak force’s of attraction allow the sheets of carbon to slide past each other which makes quite soft and useful as a lubricant

diamond has a high melting point because of many strong covalent bonds that need a lot of energy to be broken. Diamonds has four covalent bonds for each carbon atom. The carbon atoms are in a tetrahedral arrangement , joined by strong covalent bonds that gives diamond its extreme hardness and this is why it is used to make cutting tools. Graphite has a high melting point because of many strong covalent bonds that need a lot of energy to be broken.

• solids with high melting points • shiny (when polished) • malleable • high density • good conductors of electricity.

When you hit a metal, the layers of ions slide over each other. The ‘sea’ of electrons holds the ions together and so the metal changes shape instead of breaking.

Metallic bonding is the electrostatic forces of attraction between the positive metal ions and the negative sea of delocalized electron.

Mg+2 because is contributes 2 electrons to the sea of electrons while Na+ only contributes 1

Hight Melting/boiling point Solid at room temperature Malleable Conduct electricity when Solid or liquid