Answer:
nonpolar covalent bond: A covalent bond in which the bonding electrons are shared equally between the two atoms. polar covalent bond: A covalent bond in which the atoms have an unequal attraction for electrons and so the sharing is unequal.
Answer:
the answer is C + H2O # CO + H2.
Answer:
Period
Explanation:
horizontal is a period and verticle is a group
Answer: The correct option is 3.
Explanation: We are given a compound which is made up of iron and oxygen only. The ratio of the two are given as:

This means that, number of iron ions are 2
Number of oxide ions are 3
From the above information, the formula becomes : 
The valency of iron = 3
Valency of oxide = 2
This compound is named as iron (III) oxide.
Hence, the correct option is 3