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:
Major Plates
Africa Plate
Antarctic Plate
Indo-Australian Plate
Australian Plate
Eurasian Plate
North American Plate
South American Plate
<span>Pacific Plate
Minor Plates
There are dozens of smaller plates, the seven largest of which are:
</span>Arabian Plate
Caribbean Plate
Juan de Fuca Plate
Cocos Plate
Nazca Plate
Philippine Sea Plate
<span>Scotia Plate</span>
Answer:
In the n = 3 energy level
Explanation:
There's is no further explanation for this.
All the electrons in an energy level are distribuited according to the period in the periodic table they are.
So, if we have an atom in period 1, like Hydrogen (H), that atom would only have 1 level energy (n = 1) and in that level, we only have the sub level 1s.
Electrons in the 3d sublevel, are found mostly in all the transition metals of period 3, and it can go from 1 to 10 electrons. To be with the 3d sub level it's neccesary that the energy level to be 3.
energy levels beyond that, like n = 4, we have electrons occupying the 3d sub level, so, primordly, the 3d is found only in energy level 3.
Hope this helps
The moles of O2 are needed to react completely with 1.00 mol of C₂H₂ is 5 mol , 0.23 moles of C₂H₂ are needed to form 0.46 mol of CO₂ .
<h3>What is a Balanced Reaction ?</h3>
A balanced reaction is a reaction in which the number of atoms present in the reactants is equal to the number of atoms in the products.
It is given in the question that
the combustion of Acetylene is given by
2 H―C≡C―H + 5 O₂ → 4 CO₂ + 2 H₂O
Given moles of Acetylene = 1 mol
Moles of oxygen needed = 5 mol
as the mole fraction of Acetylene to Oxygen is 1 :5
The mole of Acetylene needed to form 0.46 mol of CO₂ is ?
mole fraction of CO₂ to Acetylene is 4:2
Therefore 0.23 moles of CO₂ is required.
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A substance that reduces the hydrogen ion concentration of a solution is <u>base</u>.
A base which thus completely dissociates in an aqueous solution is referred to as a strong base. These substances produce one or more hydroxide ions (OH-) per base molecule when they ionize in water. A weak base, on the other hand, only partially splits into its water-soluble ions.
The three definitions of "base" used in chemistry are Arrhenius base, Bronsted base, as well as Lewis base. The fact instead that bases react towards acids is acknowledged by all base definitions.
Therefore, a substance that reduces the hydrogen ion concentration of a solution is <u>base</u>.
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