Get it Right on Ionic/Electrovalent Bonds/Compounds in Chemistry

IONIC/ELECTROVALENT BONDS/ COMPOUNDS

An ionic/Electrovalent bonding is when a metal atom transfers or loses all valence electron(s) in its valence(outermost) shell into the valence shell of a non-metal atom in order to make both the metal and non-metal atom have an electronic configuration of a stable noble gas structure(octet structure). Through this, an ionic bond is formed between these two types of atoms, to form an ionic compound.

The periodic table as we know, consists of elements arranged in groups (elements placed in columns) and periods(elements placed in rows). The periodic table has eight(8) major groups. All the atoms of elements in group 8 are called noble/inert gases, and are importantly known for their stability, i.e not gaining, losing or sharing elections, because they have complete eight electrons(octet structure) in their outermost shell or complete two electrons(duplet structure) as only in Helium, He.

Note : Mind you that in every atom of an element, the first shell can only contain maximum of two electrons, then other shells can only contain maximum of eight electrons in each shells.

Every atom of group 1 to group 7 elements wants to become stable, i.e having the octet, or duplet structure in the case of Hydrogen, Lithium, Beryllium, and Boron. This forms the basis of octet rule which states that: An atom would always continue to lose, gain, or share electrons in order to have complete electrons in the outermost shell . This is why chemical reactions occur or take place between atoms.

This octet rule does not include atoms of group 8 elements(noble gases) because they are constantly stable_ not losing, gaining, or sharing electrons and their valence shell are completely filled with electrons, which makes them not to take part in any chemical reaction.

TO KNOW AN IONIC COMPOUND BY SIGHT:

Once you have mastered the metal and non-metal elements in the periodic table, identifying compounds that are ionic would be very easy for you.

Being that ionic bonding exists between only metals and non-metals, every ionic compound must only contain a metal(s) and also a non-metal(s) atom.

For example: In NaCl, it is made up of Sodium, which is a metal, and Chlorine, which is a non-metal. This shows that it is an ionic compound. Other examples of ionic compounds are CaF2, Al2O3, KCl, etc.

In NO2, both Nitrogen and Oxygen are non-metals, and there is no metal, which does not make it ionic but covalent.

In CO2, Carbon is a metalloid and Oxygen is a non-metal, and so not ionic.

FORMATION OF IONIC COMPOUND

All metal atoms tend to lose their valence electron(s) in its valence shell to obtain octet number of electrons in the previous shell__ While non-metal atoms gain electrons from the valence electrons lost by atoms.

Take Note : Atoms of metalloids only share their valence electrons with other atoms.

When a metal and a non-metal atom lose and gain the same number of electrons respectively, they combine or bond together to form ionic compound making them electrically neutral/stable. In other words, the metal atom transfers or loses electrons into the outermost shell of a non-metal atom, while the non-metal atom gains or receives the electrons by the metal atom.

In NaCl, Sodium atom, 11Na, 2 8 1 , has the atomic number 11, and Chlorine atom, 17Cl, 2 8 7 , having atomic number 17.

Sodium has only one valence electron while Chlorine has seven valence electrons in its outermost shell. Sodium has to lose its one valence electron to Chlorine, to form the octet structure with the electronic configuration, 2 8 , while Chlorine has to gain one more electron from Sodium to complete its shell and obtain the octet structure with the electronic configuration, 2 8 8 .

This occurrence makes the electronic configuration of Sodium ion to become like that of Neon atom, 10Ne, 2 8, which is the nearest noble gas to Sodium in the periodic table. While that of Chlorine ion electron configuration becomes like that of Argon atom, 18Ar, 2 8 8, which is the nearest noble gas to Chlorine in the periodic table. Finally bonding together, they form ionic compound.

Note: Remember that when an atom loses or gains one or more electron, it becomes an ion .

In Al2O3, Aluminum, 13Al, 2 8 3 , has the atomic number 13, and Oxygen, 8O, 2 6 , has the atomic number 8.

Aluminum has three valence electrons while Oxygen has six valence electrons. Aluminum has to lose its three valence electrons to Oxygen, and Oxygen has to gain two electrons to complete its shell, both becoming like that of 10Ne structure, 2 8, since it is the nearest noble gas to them.

Though, one Aluminum atom and one Oxygen atom have not the same total number of electrons needed to lose or gain, in completing their shells, then their atoms must be multiplied separately, in other to balance the number of electrons lost and gained.

Checking: If one Aluminum atom is to lose three electrons, then two Aluminum atoms would totally lose six electrons (2 x 3 electrons each).

For Oxygen, if one Oxygen atom is to gain two electrons, then three Oxygen atoms would totally gain six electrons(3 x 2 electrons each).

Now, the electrons can be balanced.

Combining: Two atoms of Aluminum lose a total of six valence electrons to the shells of three atoms of Oxygen, thereby forming an ionic compound.

CHARACTERISTICS OF IONIC COMPOUND

1. Ionic bonds or compounds are only formed between atoms of group 1, 2 and 3, which are metals, and atoms of 5, 6 and 7, which are non-metals.

2. When an ionic compound is dissolved in water, they dissociate (i.e split/separate) into opposite charged hydrated ions, which makes them a good conductor of electricity (electrolyte) in this state.

3. Because of their charged ions being opposite, the ions are held together by strong electrostatic force, which gives them the shape of giant crystalline solids at room/normal temperature, 250C.

4. They have high melting and boiling points due to the strong electrostatic forces holding the ions together. Ionic compounds are solid at room temperature because of strong electrostatic force holding them tightly together. For an ionic to melt or boil, the electrostatic force must be broken, which will result to change in physical start of the compound into liquid or gas.

5. In their solid state, they cannot conduct electricity because they are neutral and stable, and cannot form mobile ions. They can only be mobile ions if in their fused/molten and aqueous state.

6. They are polar, and therefore dissolve only in polar solvents like water and alcohol.