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Atoms!

Introduction :

Atoms are the simplest form of an element. Atoms exist in every material substance on Earth whether it's in the form of molecules, compounds or mixtures. The type of atom is determined by the number of protons they have and can be referenced by the periodic table. For example, an atom containing one proton is hydrogen, two is helium, three is lithium and so on. Do use the simulation below to understand further. The structure shown above is Lithium, based on its proton number.

Attribution : PhET Interactive Simulations, University of Colorado Boulder, https://phet.colorado.edu.

Electronic Structure of an Atom :

Electrons are negatively charged and are attracted to the nucleus because of the protons. These sub-atomic particles located on electron shells are drawn apart as like charges repel. The max number of electrons for each shell can be summarised by the formula 2n².

Electron Shell	Max Electrons (2n²)
1st	2
2nd	8
3rd	8 or 18
4th	8 or 32

Electronic Structure Example 1 (Lithium) :

We know lithium has 3 protons so, the atom should also have 3 electrons. Since the maximum number of electrons in the first shell is 2, we have 1 extra electron for the second shell. This means the electronic configuration is 2.1 which can be drawn as follows :

Electronic Structure Example 2 (Chlorine) :

We know chlorine has 17 protons so, the atom should also have 17 electrons. Since,

1. The maximum number of electrons in the first shell is 2, we have 15 extra electrons

2. From the 15, we can only place 8 in the second shell which fills it to its maximum and leaves us with 7 electrons left

3. We can place all 7 electrons in the third shell as we did not exceed the maximum of 8 electrons

This means the electronic configuration is 2.8.7 which can be drawn as follows :

Combining atoms :

1. If more than one atom is chemically combined together, we get molecules

2. If different types of atoms are chemically combined together, we get compounds which are also molecules

3. If there is only one type of atom, regardless of the number of atoms present, we get an element.

Do try out the simulation below to test your knowledge.