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:
This is true otherwise cancer patients would have a hole in them and so would the hulk ;)
Answer: D. They show that neither theory is complete and entirely correct.
Explanation:
Theory is the set of rules and principles that describe and explain a particular phenomenon (the existence of the moon in this case) and is subject to changes as new evidence emerges that gives meaning to it.
In this sense, there are many theories about the Earth's moon formation and two of the "accepted" theories are described before the question. In addition, both theories explain in a certain way the reason why the Moon is predominantly composed of elements similar to those found on Earth.
However, both theories seem to be incomplete when trying to explain our Moon's origin.
There are several ways to give an object potential energy. One can move the object against the force of gravity to increase. One can also stretch an object out or put pressure on it.
