ANSWER:
4 a) Specific elements have more than one oxidation state, demonstrating variable valency.
For example, the following transition metals demonstrate varied valence states: 
, 
, 
, etc.
Normal metals such as 
also show variable valencies. Certain non-metals are also found to show more than one valence state 
4 b) Isotopes are members of a family of an element that all have the same number of protons but different numbers of neutrons.
For example, Carbon-14 is a naturally occurring radioactive isotope of carbon, having six protons and eight neutrons in the nucleus. However, C-14 does not last forever and there will come a time when it loses its extra neutrons and becomes Carbon-12.
5 a) 
→ 
5 b) 
→ 
5 c) 
→ 
(already balanced so don't need to change)
5 d) 
→ 
5 e) 
→ 
EXPLANATION (IF NEEDED):
1. Write out how many atoms of each element is on the left (reactant side) and right (product side) of the arrow.
2. Start multiplying each side accordingly to try to get atoms of the elements on both sides equal.
EXAMPLE OF BALANCING:
Explanation:
the tip of a growing plant contains special rapidly diving cells called apical meristem ,these cells are responsible for increase in the length of the plant . if we cut out these cells ,length growth of the plant will be stunned as these cells are not present anyplace else.
A. They were ways Congress sought to guarantee blacks the full rights of citizenship.
Actually, that does not happen until the protostar becomes a star when nuclear ignition starts and is maintained. It takes awhile for new star to go through its T-Tauri stage and settle down on the main sequence.
<span>A STAR does not reach hydrostatic equilibrium until it on the main sequence. Otherwise, it would remain a brown dwarf with not enough mass to to maintain nuclear fusion for more than 3,000 to 10,00 years. </span>
You can tell if each side of the equation has the same molar mass.
