Chemistry » Essential Ideas in Chemistry » Electronic Configuration

Importance of Understanding Configuration

The Importance of Understanding Electron Configuration

By this stage, you may well be wondering why it is important for you to understand how electrons are arranged around the nucleus of an atom. Remember that during chemical reactions, when atoms come into contact with one another, it is the electrons of these atoms that will interact first. More specifically, it is the valence electrons of the atoms that will determine how they react with one another.

To take this a step further, an atom is at its most stable (and therefore unreactive) when all its orbitals are full. On the other hand, an atom is least stable (and therefore most reactive) when its valence electron orbitals are not full. This will make more sense when we go on to look at chemical bonding in a later chapter. To put it simply, the valence electrons are largely responsible for an element’s chemical behaviour and elements that have the same number of valence electrons often have similar chemical properties.

The most stable configurations are the ones that have full energy levels. These configurations occur in the noble gases. The noble gases are very stable elements that do not react easily (if at all) with any other elements. This is due to the full energy levels. All elements would like to reach the most stable electron configurations, i.e. all elements want to be noble gases. This principle of stability is sometimes referred to as the octet rule. An octet is a set of 8, and the number of electrons in a full energy level is 8.

Informal Experiment: Flame Tests


To determine what colour a metal cation will cause a flame to be.


  • Watch glass

  • Bunsen burner

  • methanol

  • tooth picks (or skewer sticks)

  • metal salts (e.g. \(\text{NaCl}\), \(\text{CuCl}_{2}\), \(\text{CaCl}_{2}\), \(\text{KCl}\), etc.)

  • metal powders (e.g. copper, magnesium, zinc, iron, etc.)


Be careful when working with Bunsen burners as you can easily burn yourself. Make sure all scarves/loose clothing are securely tucked in and long hair is tied back. Ensure that you work in a well-ventilated space and that there is nothing flammable near the open flame.


For each salt or powder do the following:

  1. Dip a clean tooth pick into the methanol

  2. Dip the tooth pick into the salt or powder

  3. Wave the tooth pick through the flame from the Bunsen burner. Do not hold the tooth pick in the flame, but rather wave it back and forth through the flame.

  4. Observe what happens


Record your results in a table, listing the metal salt and the colour of the flame.


You should have observed different colours for each of the metal salts and powders that you tested.

The above experiment on flame tests relates to the line emission spectra of the metals. These line emission spectra are a direct result of the arrangement of the electrons in metals. Each metal salt has a uniquely coloured flame.


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