Consider the elements Ca, I, S and Se. Which one would be most likely to form a 2+ ion?

Question

Consider the elements Ca, I, S and Se. Which one would be most likely to form a 2+ ion?

Answer 1

You need to relate the type of ion formed to the group of the Periodic Table.

Group I (Li, Na, K etc) have one outer shell electron and lose one when they react, this leaves them with a +1 charge (one more proton than electrons)

Group II (Be, Ca, Mg etc) have two outer shell electrons so when they lose these end up with a +2 charge

Group III (B, Al etc) have +3 ions

Group IV (C, Si etc) generally bond covalently so don't have ions (apart from near the bottom of the group)

Group V (N, P etc)have 5 outer electrons and GAIN 3 to fill the shell as they bond so their ions have a -3 charge (3 more electrons than protons)

Group VI (O, S etc) have -2 charged ions

Group VII (F, Cl, Br etc) have -1 charged ions

the pattern left to right goes +1, +2, +3, None, -3, -2, -1 so is easy to remember.

Hope this helps

Answer 2

You really shold know this, you can't ask me when you are in the exam hall!

    What are some common compounds of these elements?  Are they ionic compounds, or covalently bonded?  Don't look for an easy answer, understand how to get the answer, or you aren't learning anything, and should drop chemistry.

Answer 3

2Ca-

Answer 4

Calcium

Answer 5

Only Ca will form the 2+ ion.

Iodine forms the 1- ion

Sulphur forms the 2- ion

Selenium forms either the 4+ or 4- ion depending on the other reacting materials

Answer 6

Calcium is a Group 2 (alkaline earth metal) and has only two valence electrons.  Calcium loses these two valence electrons to form a 2+ ion.  The other elements are nonmetals, and as such form ions by gaining enough electrons to form a stable octet and negatively charged ions.

Answer 7

Calcium.  But you need to research why.