Chemical bonding! help!

[cherylwhoa]

Hi. i'm a student who does not get anything about chemistry.
we are having a test soon on covalent bonding and ionic bonding. and i just don't get it, since i haven't learned anything about chemicals, the periodic table, etc. at my old school.

Here are some questions from a study worksheet that my teacher gave me:
1) which of the following is NOT a polyatomic ion?

• A > carbonate ion
  B > hydroxide ion
  C > iodide ion
  D > sulphate ion

2) Which of the following elements is likely to react with hydrogen, forming a compound with chemical formula XH3?

• A > phosphorous
  B > sulphur
  C > chlorine
  D > Carbon

3) an element M (atom with electronic arrangemetn 2,8,8,1) combines with an element X (atom with electronic arrangement 2,8,7) to form a compound Y. The chemical formula of Y is:

• A > MX2
  B > M2X
  C > MX
  D > M2X2

these were just a few of the questions that i didn't get.
thanks so much!!

[salaka]

Originally Posted by cherylwhoa

Hi. i'm a student who does not get anything about chemistry.
we are having a test soon on covalent bonding and ionic bonding. and i just don't get it, since i haven't learned anything about chemicals, the periodic table, etc. at my old school.

Here are some questions from a study worksheet that my teacher gave me:
1) which of the following is NOT a polyatomic ion?

• A > carbonate ion
  B > hydroxide ion
  C > iodide ion
  D > sulphate ion

2) Which of the following elements is likely to react with hydrogen, forming a compound with chemical formula XH3?

• A > phosphorous
  B > sulphur
  C > chlorine
  D > Carbon

3) an element M (atom with electronic arrangemetn 2,8,8,1) combines with an element X (atom with electronic arrangement 2,8,7) to form a compound Y. The chemical formula of Y is:

• A > MX2
  B > M2X
  C > MX
  D > M2X2

these were just a few of the questions that i didn't get.
thanks so much!!

1)It would be C, I beleive. I could be wrong but polyatomic ion means what it is saying, poly=many and atomic ion. So which one is NOT a polyatomic ion is easy to find out. Carbonate has the eqaution of CO3 which contains two different elements (4 in total). Hydroxide has the equation of OH which contains two elements to form an ion. Iodide is just Iodine in its ion state, so it only has one element. And sulfate has the equation of SO4. Your teacher should have given you an ion sheet of multiple ions (atleast mine did), this will help you alot.

2)I would have to say A, mainly because phosphorus reacts to take 3 electrons from those three hydrogen molecules. However it may be Carbon because there is a hydrocarbon of CH3.

And the last one just confuses me.

I had trouble with chemistry too (I got put in a CP chem class without that much advanced knowledge in science or even advanced math).

[Hix3r]

What was said before, first one is C, no doubt. Iodide ion is I- a monoatomic ion.

Second one is indeed A. Phosphorus need 3 electrons to reach noble gas state, and 3 hydrogen is required for that. The substance is PH3 or phosphine gas, a toxic gas.
Carbon forms methane CH4! Sulfur forms SH2 which is tha substance why rotten eggs smell bad. Chlorine forms HCl, hydrochloric acid, which is well known.

Third one is C. No question. The 2, 8, 8, 1 electron configuration is potassium, and the 2, 8, 8, 7 is Bromine. The formed substance is KBr, potassium-bromide. You can guess is simply though. The 2, 8, 8, 7 atom needs one electron more to reach noble gas state, which is 2, 8, 8, 8(Kripton). The other othe needs to give away an electron to reach again noble gas state, which is 2, 8, 8(Argon). So it has to be MX configuration, they only need each other.