2 ionic bonding questions

[amerfarooq]

Q.1 Write the symbol of 3 particles that have only 2 electrons.
I can write He and H2. What could be the third one ?

Q.2 Element X reacts with bromine to from an ionic compound XBr2.
a) Is X a metal or a non metal ?
b) Deduce the charge of the Ion X in the compound XBr2
c) What is the formula of the oxide formed when X reacts with oxygen ?

From what I've understood Xbr2 means there is only 1 X ion and 2 Bromine Ions. The electronic configuration for bromine in 2,8,18,7. So does bromine take another 25 electrons or will it lose its 7 ? And if their are 2 of these ions then the total electrons to be transferred are 14 and if X is only a single ion it has to fill all those 14 electrons in its valence shell. What element can do that ? I'm confused, just started bonding for the first time.

 

[dragonheartstring]

Q1. The third one could be Li+ I think...

For question 2.
I don't know if you've heard of the criss-cross rule when writing the formula for compounds, but that's basically how you'd solve this question. Basically, when you write the formula for ionic compounds, you swap the charges on the relative elements and they become the subscripts for the new compound. This probably makes no sense so let me give you an example.
If I wanted to see what the formula is for Lithium Sulphide, I'd look at the charges of each of the two elements. Lithium is +1 and Sulphur is +2. So you criss cross the charges and you end up with: LiS2. Likewise, if I wanted to write the formula for Aluminium Oxide, I'd write down the charges for the two elements: Al +3 and O +2 and then I'd swap the charges to get Al3O2.

a) This is relatively easy to answer. The compound is ionic so X is obviously a metal because ionic compounds only occur between metals and non metals and the non metal is the Bromine.
b) Using what I showed you above ^^ you should be able to find that the charge of Ion X is +2 ; + because it's a metal and 2 because after the criss cross rule, the Bromine has a subscript of 2.
c) You already know that the charge of Ion X is +2 from question B and you know that the charge of Oxygen is -2- both of the charges cancel each other out so you just end up with XO.

You're right in thinking that one atom of X bonds with 2 Bromine molecules. However, for a bromine to get a complete shell, it gains one electron- it doesn't lose seven. So if you have two bromine electrons, then both of them need to gain one electron. This means that in total, the metal they will be bonding with is a metal that will need to lose 2 electrons (one of which will be given to each bromine). The metals which lose 2 electrons to get complete shells are those metals found in Group 2- metals such as Magnesium or Calcium.

 

[amerfarooq]

Thank you for replying but i eventually figured it out myself. Why i wasn't getting the answer in the first place was because i thought the electronic configuration of Bromine being 2,8,18,7 meant it had to loose 7 electrons because the 4th shell has 32 electrons and so X with the subscript 1 would have to be a metal that could take 7 electrons but metals don't take they give and blah blah blah..... But thanks for answering anyway

 

[adil]

^^ you mentioned the criss cross technique but you did it wrong in both examples, in LiS you said Li has +1 charge and S has +2 (which actually is -2) but still you did not criss cross the values you said the answer would be LiS2 (which should have benn Li2S because only this the compound is stable) similarly you made those mistake in example two as well firstly you mentioned oxygen's oxidation state as +2 which instead is -2 and the answer in Al2O3 not Al3O2 as you mentioned it.

 

[Hamza Khan]

For Q2.
a) Metal
b) +2. As One X Combines With 2 Bromides To Produce XBr2 And We Know That The Valency Of Bromide Ions Is -1 So The total charge on Bromine = -1 x 2 = -2....
So we can deduce that X Must have A Valency Of 2+ ... We can also cross their valencies to check the answer ... X2+ Br-1 ... By Crossing Then We Get XBr2
c) As We Figured out the valencie of X Is the Above part ... we can simply cross their valencies ... X2+ O2- = X2O2 .. As We Can deduce that they are combining in the ratio of 1:1 ... The Formula Of X's Oxide Must be ... XO ...
.....
Hope This Helps..