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C2 Structure and Bonding

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Structure and Bonding
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Keywords

Bond

An interaction between two atoms either due to an electrostatic force, or the sharing of electrons.


Ion

An atom that has either lost or gained electrons forming a positively charged substance or negatively charged, respectively.

Forming Bonds

All atoms want a full outer shell of electrons (all atoms need 8, except H & He that want 2). This is a stable state. They achieve this by forming chemical bonds with other atoms.


An element’s group number tells you how many electrons are in its outer shell, and you can work out how many it needs to fill the shell.


You are only expected to be able to work with the first 20 atoms of the periodic table.

Information on the first 20 elements

Ionic Bonding

A bond that forms between a metal and a non-metal.


Metals always form positive ions (oxidised/lose electrons to form cations). A group 2 metal forms a 2+ ion (loses two electrons). Non-metals form negative ions (reduced/gain electrons to form anions).

Strong, electrostatic forces hold ions of opposing charges together. The structure is described as an ionic lattice. The compounds have very high melting points because of this.

Information on what charges ions form

Covalent Bonding

Non-metal atoms bond by sharing electrons to form a very strong covalent bond.


Two electrons are needed to make one covalent bond.


Giant Covalent

Most covalent substances are small, simple molecules of only a few atoms. Some covalent structures are much larger, and consist of a network of covalent bonds: these are giant structures.


Diamond is an example where each carbon is bonded to four other carbon atoms, resulting in a rigid giant lattice.

3D Structure of Diamond

Metallic Bonding

Metals are another example of giant structures.

Higher

They are a lattice of positively charged ions held together by a “sea of negatively charged delocalised electrons” from the outer shells of the metal atoms.

The strong electrostatic forces between the ions and electrons mean metals have very high melting points.

The free electrons are able to move through the metal, making metals good conductors of electricity and heat.

Diagram showing metallic bonding

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Page last updated: 14/04/2017