Chemistry » Bonding and Atomic Combinations » Chemical Bonds Continued

Why do atoms bond?

Chemical Bonds: Why do atoms bond?

As we begin this section, it’s important to remember that what we will go on to discuss is a model of bonding, that is based on a particular model of the atom. You will remember from the discussion on atoms (in Grade \(\text{10}\)) that a model is a representation of what is happening in reality. In the model of the atom that you are learnt in Grade \(\text{10}\), the atom is made up of a central nucleus, surrounded by electrons that are arranged in fixed energy levels (sometimes called shells). Within each energy level, electrons move in orbitals of different shapes. The electrons in the outermost energy level of an atom are called the valence electrons. This model of the atom is useful in trying to understand how different types of bonding take place between atoms.

Tip:

A model takes what we see in the world around us and uses that to make certain predictions about what we cannot see.

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Electron arrangement of a fluorine atom. The black electrons (small circles on the inner ring) are the core electrons and the white electrons (small circles on the outer ring) are the valence electrons.

The following points were made in these earlier discussions on electrons and energy levels:

  • Electrons always try to occupy the lowest possible energy level.
  • The noble gases have a full valence electron orbital. For example neon has the following electronic configuration: \(1\text{s}^{2}2\text{s}^{2}2\text{p}^{6}\). The second energy level is the outermost (valence) shell and is full.
  • Atoms form bonds to try to achieve the same electron configuration as the noble gases.
  • Atoms with a full valence electron orbital are less reactive.

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