| | Chemical bondings | Chemical bondings take place between elements.When an element reacts with another element,it tends to gain or lose electrons.When an element loses electrons,it becomes positively charged and when it gains electrons,it becomes negatively charged.
An element is defined as the smallest indivisible part of a substance.In other words,it cannot be broken or split into two or more simpler substances. | | | | When an element of sodium reacts with another element of chlorine,the sodium element becomes positively charged while the chlorine element becomes negatively charged.This happens because the sodium has lost electrons to the chlorine element to become positively charged while the chlorine element has gained electrons to become negatively charged.This behaviour can be seen in their electronic configurations.Sodium has two electrons in the innermost shell,eight electrons in the first shell and one electron in the second shell,making the nucleus of sodium which is made up of protons and neutrons to contain 23 units.Sodium is electrically neutral because it contains the same number of protons and electrons.The numbers of protons and electrons in sodium are both 11. | | | Similarly,chlorine has two electrons in the innermost shell,eight electrons in the first shell,and seven electrons in the second shell,making the nucleus to contain 17 units.Chlorine is also electrically neutral because it contains the same numbers of protons and electrons.
After chemical bonding,sodium now has two electrons in the innermost shell,and eight electrons in the first shell whereas,chlorine has two electrons in the innermost shell,and eight electrons in the first shell and another eight electrons in the second shell.
This type of bonding is called Electrovalent bonding.It is the transfer of electrons between elements.Sodium and chlorine electronic configurations can be depicted as follows: | | | Before chemical bonding.
Na Cl
2,8,1 2,8,7
After chemical bonding.
Na+1 Cl-1
2,8 2,8,8
| | | The aforesaid bonding takes place between a metal and a non-metal.But there are instances when chemical bonding takes place between two non-metals.In such case,electrons are not transferred but they are shared.When electrons are shared between two elements,the type of bonding that is existing between them is called Covalent bonding.Taking chlorine molecules-Cl2 and methane-Ch4 for instance.
Electrons are not transferred between the elements of chlorine molecules but they are shared,and similarly,in the methane molecules.Their electronic configurations before and after bonding are as follows: | | | Before bonding
Cl Cl
2,8,7 2,8,7
After bonding
Cl • Cl --Cl2 (Chlorine molecules)
2,8,8 2,8,8
In the case of methane,one element of carbon reacts with four elements of hydrogen to form a methane molecule. |
|
| |
