Chemical Bond

Electronegativity values are useful in predicting how electrons will be shared. Electronegativity is a measure of the attraction an atom involved in a covalent bond…

Ionisation enthalpy is the energy required to remove a mole of electrons from a mole of free gaseous atoms i.e. the energy required to remove…

The melting point starts off low, gradually increases to a peak (at group 14) then gradually decreases to a very low value (at group 0…

The density of a substance is its mass per unit volume, usually measured in g cm. The graph below shows the variation in density (at…

In a modern Periodic Table the elements are written in order of increasing atomic number, not increasing R.A.M. This leads to Periodic law which states…

Dobereiner’s “triads” (1829) where groups of three similar elements were made such as Li, Na, K; Ca, Sr, Bo; or Cl, Br, I This was…

Inter molecular forces are weak, so the molecules are not pulled very close together. More space between the molecules means that solid simple molecular compounds…

Simple molecules Most covalently bonded substances exist as simple small or medium sized molecules, rather than as giant structures. When simple molecules are heated moderately,…

Fullerenes are a recently discovered family of carbon allotropes in the form of spheres, tubes or flat planes with unusual and potentially useful properties. The…

Graphite (the “lead” inside pencils) is another allotrope of carbon. Each carbon atom is joined by strong covalent bonds to three others, forming sheets of…