Chemistry [3 Mark Question Answer]

Properties of Covalent Compounds:
1. The covalent compounds exist as gases or liquids or soft solids.
2. The melting and boiling points of covalent compounds are generally low.
3. Covalent compounds are insoluble in water but dissolve in organic solvents.
4. They are non-conductors of electricity in solid, molten or aqueous state.

Properties of Ionic Compounds:
1. Ionic compounds usually exist in the form of crystalline solids.
2. Ionic compounds have high melting and boiling points.
3. Ionic compounds are generally soluble in water but insoluble in organic solvents.
4. They are good conductors of electricity in the fused or in aqueous solution state.

The crystalline solid is ionic in nature. It has strong electrostatic forces of attraction between its ions, which cannot be separated easily.
Crystalline solids have high melting and boiling points, and a large amount of energy is required to break the strong bonding force between ions.
Water is a polar compound, so it decreases the electrostatic forces of attraction in the crystalline solid, resulting in free ions in the aqueous solution. Hence, the solid dissolves.

Ionic compounds, made up of ions, are generally crystalline solids with high melting and boiling points.
They are soluble in water and good conductors of electricity in aqueous solution and molten state.
Covalent compounds, made up of molecules, can exist as soft solids or liquids or gases with low melting and boiling points. They are generally insoluble in water and poor conductors of electricity.

Conditions for formation of Ionic bond are:
(i) The atom which changes into cation should possess 1, 2 or 3 valency electrons. The other atom which changes into anion should possess 5, 6 or 7 electrons in the valence shell.
(ii) A high difference of electronegativity of the two atoms is necessary for the formation of an Ionic bond.
(iii) There must be an overall decrease in energy i.e., energy must be released. For this an atom should have low value of Ionisation potential and the other atom should have high value of electron affinity.
(iv) Higher the lattice energy, greater will be the case of forming an ionic compound.

This means that in the water molecule, one side is positively charged and the other side is negatively charged.
Explanation:

Electrovalent compounds have a strong force of attraction between the oppositely charged ions, so a large amount of energy is required to break the strong bonding force between ions. So, they have high boiling and melting points.
Covalent compounds have weak forces of attraction between the binding molecules, thus less energy is required to break the force of binding. So, they have low boiling and melting points.

Chlorine atom and chlorine ion
(i) Chlorine atom has 7 electrons in its M shell while Chloride ion has 8 electrons in the same shell.
(ii) Chlorine atom is neutral while chloride ion is negatively charged.
(iii) Chlorine atom is highly reactive while its ion is inert.
iv) Chlorine gas is poisonous while chloride ion is non-poisonous.

Sodium atom and sodium ion
(i) Sodium atom has one electron in M shell while sodium ion has 8 electrons in L shell.
(ii) Sodium atom is neutral while sodium ion is positively charged.
(iii) Sodium atom is highly reactive while its ion is inert.
(iv) Sodium atom is poisonous while sodium ion is non-poisonous.

Ca - will donate two electrons
O - will accept two electrons
Cl - will accept one electron, so two Cl atoms will share an electron pair.
C - will accept four electrons by sharing electrons pairs with hydrogen forming covalent bonds.
H - will donate one electron by sharing an electron pair with carbon.