Helium
Remember: electron filling of atomic shell ...
The element which have electron in the lowest quantum shell will have the smallest atomic radius\
He:1s1 (Helium)
H:1s2 (hydrogen)
Answer: 4 and 6
Explanation: the double bonds are alternating in the chain
C—C=C—C=C—C=C—C=
1 2 3 4 5 6 7 8
6.022*10^23 molecules
4*6.022*10^23 atoms = 24.08*10^23 atoms
One mole of CS₂ and two moles of H₂S are formed as products and 3 moles of CH₄ are leftover.
<h3>What is the limiting reagent?</h3>
A limiting reagent is a reactant that is fully exhausted from the reaction mixture at the completion of a reaction. The limiting reactant will decide the maximum amount of product.
Given, a balanced chemical equation of the reaction between methane and sulphur is:

Given, the number of moles of the sulphur = 4
The number of moles of methane = 4
From the chemical reaction, one mole of methane reacts with four moles of sulphur. Therefore, four moles of sulphur fully react with one mole of methane and three moles of methane leftover.
Learn more about limiting reagents, here:
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Epsom salt is MgSO4.
We assume x water of hydration in the crystalline form.
Molecular mass of MgSO4 = 24+32+4*16=120
Molecular mass of MgSO4.xH2O = 120+18x
By proportion,
2.000/0.977 = (120+18x)/120
Cross multiply
0.977(120+18x) = 120*2.000
from which we solve for x
17.586x+117.24 = 240
x=122.78/17.586
=6.980
Answer: there are 7 water of hydration in Epsom salt, according to the experiment.
Note: more accurate (proper) results may be obtained by using exact values (3-4 significant figures) in the molecular masses. However, since water of hydration is the nearest integer, using approximate values (to at least two significant figures) suffice.