chemistry chapter 5:form 4

Duplet and Octet arrangment

The charge on the nucleus and the number of electrons in the valence shell determine the chemical properties of an atom

The stability of noble gas is due to their electrons arrangement.

The diagram above shows the first four elements of Noble Gas.

We can see that the valence shell of Helium has 2 electrons. We call this duplet electron arrangement. We should take notes that the maximum number of electrons can be filled in the first shell is 2 electrons, which means 2 electrons in the first shell is considered FULL.

The valence shell all other Group 18 elements (including Xenon and Radon which is not shown in the diagram) has 8 electrons, and we call this octet electron arrangement.

When the electron arrangement of an atom is duplet or octet, the energy of the electrons is very low, and it is very difficult (even though it is not impossible) to add or remove electrons from the atom.

How Atoms Achieve Duplet or Octet Electron Arrangement?

Atoms can achieve duplet or octet electron arrangement in 3 ways:

1.throw away the excess electron(s)

2.receiving electron(s) form other atom if they are lack of electron(s)

3.sharing electron

2 types of chemical bonds are commonly formed between atoms, namely

a]Ionic Bond

b]Covalent Bond

The Ionic Bond
By releasing or receiving electron(s), the atoms will become ions and consequently form ionic bond between the ions.

Ionic bonds are always form between metal and non-metal. For example, sodium (metal) react with chlorine (non-metal) will form an ionic bond between sodium ion and chloride ion.

The compounds formed is called the ionic compound.
Some time, an ionic bond is also called electrovalent bond.
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The Covalent Bond
By sharing electron(s), the atoms will form covalent bond between the atom and the molecule formed is call the covalent molecule.

Covalent bond is always formed between non-metal with another non-metal