Can you explain these chem. answers?

Question

1) The balanced equation below represents a molecule of bromine separating into 2 bromine atoms.

Br2 --> Br + Br

What occurs during this change.

Answer is energy is absorbed and a bond is formed.

2) Which compound is insoluble in water?

-BaSO4 -CaCrO4 -KClO3 -Na2S

Answer is BaSO4

3) What is the total number of pairs of electrons shared in a
molecule of N2?
Answer = 3.

**All the numbers are subscripts.

Answer 1

1) Bromine is in a more stable state when it is a diatomic molecule. Therefore, in order to split the molecule apart into the separate atoms energy must be added. Bromine molecules (Br2) allow the electrons to be shared and to help each atom in the pair to have an electron configuration of a noble gas. The single Br atoms have only 7 electrons in their valence level, so they want to react with anything around them to get to the valence state of a noble gas.

2) You would need to refer to a table of solubility rules for this one. Sulfates are generally soluble in water, but BaSO4 is one of the exceptions to this rule. I am sure your text can help you with the solubility rules, or there are numerous sites on line to help you.

3) N is in group 5A. This means it has 5 valence electrons. Its electron configuration is 1s2, 2s2, 2p3 - where the 2s2 and 2p3 electrons are the valence electrons. That means it needs to either bond covalently 3 times to get up to a valence of 8 electrons like the nearest noble gas (Ne) or it can gain 3 electrons to get up to a valence of 8 like Ne. When two N join to make N2 they must form covalent bonds. The 2p3 electrons of each atom join (3 bonds to one other atom make this a triple covalent bond).

Answer 2

0, elements do ot have charges -2, oxygen is always -2 in a compound +3, SO4 always has a charge of -2, compounds do not have a charge +6, SO4 is -2, oxygen is always -2, if the O is -8,the S must be +6

Answer 3

1. The bond is broken in this reaction. But it probably took energy to break it.