Electronegativity Value and Bonding
Chemistry

Electronegativity Value and Bonding

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
Chemistry

Ionisation Enthalpy

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…
Melting Points in Modern Periodic Table
Chemistry

Melting Points in Modern Periodic Table

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…
Density in Modern Periodic Table
Chemistry

Density in Modern Periodic Table

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…
Modern Periodic Table
Chemistry

Modern Periodic Table

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…
Historical Trends Trends in the Periodic Table
Chemistry

Historical Trends Trends in the Periodic Table

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…
Properties of Simple Molecules
Chemistry

Properties of Simple Molecules

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 Molecular Structures
Chemistry

Simple Molecular Structures

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 Molecular Structure
Chemistry

Fullerenes Molecular Structure

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 Molecular Structure
Chemistry

Graphite Molecular Structure

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…
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