Chemistry Michaelmas Test

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  • Created by: Livy
  • Created on: 16-11-13 14:43

Atomic Structure

Protons and Neutrons are found in the Nucleus. Electrons orbit the Nucleus in shells. The first shell holds two electrons and the other holds eight. Atomic number is the number of Protons, and the Mass number is the number of Protons and Neutrons. Isotopes are atoms with the same number of Protons but different number of Neutrons. You can compare the mass of atoms using the Relative Atomic Mass. Protons have a positive charge, and Electrons have a negative charge. Neutrons have a neutral charge because the number of Protons and Electrons are the same. 

You can work out the Relative Atomic Mass by the mass of the isotope times the mass of the atom. Then you divide by the mass of isotopes in 100 atoms in mixture. 

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Covalent Bonding Simple

Covalent bonding occurs between a non metal and a compound(2 atoms.) It occurs between two orbitals and it form covalent bond. Non metals have in complete outer shells. Only groups 1-7 can perform a covalent bond. The inner shells do not have to be included in diagrams. Covalent bonds are a result of electrostatic attraction between the positive nucleus, and the negative shared electrons. 

Double bonds are two shared pairs of electrons, and triple bonds are three shared pairs of electrons. These occur when more then one pair of orbitals overlap. Multiple bonds are stronger then single bonds. 

A non-bonding pair is a lone pair. Oxygen atoms form two bonds and have 2 lone pairs. 

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Covalent Bonding Giant Structures

In a compound, the proportions are always the same. In a mixture each element still has it's own properties, but the properties of a compound are quite different. Mixtures can be separated by physical means like the temperature or by dissolving part of the mixture in a solvent such as water. IF you mix hydrogen and oxygen there is no temperature change. If you combine hydrogen an oxygen to make water, a huge energy release occurs.When you make a compound, energy changes are much greater. 

Diamond is a form of pure carbon, in a diamond each carbon atom bonds to four other carbon atoms in a tetrahedral arrangement. This is a giant covalent structure. It continues on to the 3D. It isn't a molecule because the number of atoms in a real diamond are variable. Diamond is very hard, with a very high mpt and bpt. It is not a conductor because it has very strong covalent bonds. 

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Simple Covalent Structures

Carbon dioxide doesnt conduct electricity, covalent molecules do not conduct electricity as their particles are not charged. Inter molecular forces are forces of attraction between molecules, and they affect the mpt and the bpt of simple molecular structures, because they are easy to break. Van der Waals are intermoleclar forces. They are weak. Sand, Diamond and Graphite have millions of atoms joined by covalent bonds. Then bonds in these substances do not form molecules, but vast networks of atoms called giant covalent structures. The giant network is called the lattice. All the bonds are covalent, so giant lattices have a very high mpt and bpt and are usually hard. 

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