Answer:
Electronegativity increases across the period on a periodic table.
Explanation:
Electronegativity is the ability of an atom to attract electron to itself.
All elements on the periodic table combines in order to have a complete octet i.e they all want to be like the noble gases, group 0 elements.
This is what drives most atom to combine chemically. By so doing, they either lose or gain electrons.
Cl belongs to the 7th group on the periodic table. It is the second element in this halogen group. Most halogens are notable for their high electronegativity. They have 7 electrons in their outermost shell and would require just an electron to complete their octet.
This makes them highly reactive and combine readily with other elements.
The halogens have a strong attraction for valence electrons. The higher the electronegativity value, the stronger the attraction an atom has for valence electrons.
Most metals like Al and Na are electropositive and readily donates or lose electrons so as to have a complete octet.
Answer:
The atomic radius corresponds to Sigma
Explanation:
It is the Van Der Waals radius ;)
Nuclear energy comes from splitting of Barium atom to form Krypton atom
Answer: 
Explanation:
Entropy is the measure of randomness or disorder of a system.
A system has positive value of entropy if the disorder increases and a system has negative value of entropy if the disorder decreases.
1. 
As 4 moles of gaseous reactants are changing to 2 moles of gaseous products, the randomness is decreasing and the entropy is negative
2.
As 9 moles of gaseous reactants are changing to 10 moles of gaseous products, the randomness is increasing and the entropy is positive.
3.
As 1 mole of solid reactants is changing to 2 moles of gaseous products, the randomness is increasing and the entropy is positive.
4.
As 4 moles of gaseous reactants is changing to 5 moles of gaseous products, the randomness is increasing and the entropy is positive
5. 
As 4 moles of gaseous reactants is changing to 1 moles of gaseous products, the randomness is decreasing and the entropy is negative.
