Fill in the blanks.

1. An __________ cannot exist independently.
2. A __________ is the smallest unit of an element or a compound consisting of a group of atoms. 
3. A  water molecule contains one atom of __________ and two atoms of __________.
4. Atoms always combine in __________ to form a molecule. 
5. When two or more atoms of different elements combine in a definite proportion by mass, a __________ is formed. 

Answer in one word/ a few words. 

1. The number of atoms joined together to form a molecule of an element. 
2. The combining capacity of an element.
3. Valency of magnesium. 
4. A charged particle that carries a positive or negative charge.
5. A group of atoms of different elements functioning together as a single unit and carrying a charge.
6. Representataion of carbonate radical 

Match the columns. 

Write the names of the ions formed by the following elements and state how they are represented. 

Write the chemical formulae of the following compounds. 

1. Common salt - 
2. Copper sulphate - 
3. Hydrochloric acid - 
4. Nitric acid - 
5. Sodium carbonate -
6. Nitrogen dioxide -