how ions are formed.. i think that i’ve lost an electron. what do you mean ?

How ions are formed.

I think that I’ve lost an electron.

What do you

mean?

It just feels like something is

missing!

Are you sure

?

I’m positive!

Neutral atoms have the same number of positive

protons as they have negative electrons.

If an atom gains or loses electrons there is an

imbalance of charge, ad it is called an ION.

If only I could get rid of this spare electron in my outer shell. Then I’d be as cool as

neon.

I just need one more electron to complete my outer shell. Then I’d be just like that

dude argon.

What type of ions will be formed if Na gives its electron to Cl?

You will form a Na+1 ion when the sodium atom loses its electron, and a Cl-1 ion when the

chlorine atom gains its extra

electron.

Who will take my two spare electrons?

We will!!

What type of ions will be formed if

Mg gives its electrons to the Cl’s?

You will form a Mg+2 ion when the magnesium atom

loses its electrons, and two Cl-1 ions

when the chlorine atoms each gains

one electron.

He He. While calcium isn’t looking I can steal his two outer electrons. He He.

He He. While calcium isn’t looking I can steal his two outer electrons. He He.


O takes two electrons from Ca?

You will form a Ca+2 ion when the

calcium atom loses its two electrons,

and an O-2 ion when the oxygen atom gains two extra electron.


All 6 electrons from Al are evenly

Shared amongst the three O’s?

You will form two Al+3 ion when the aluminium atoms

lose their electrons, and three O-2 ion

when each oxygen atom gains two extra electrons.

In the examples that we’ve looked at so far,

•Do metals form positive or negative ions? ___________________________

•Do non-metals form positive or negative ions? ___________________________


•Do metals form positive or negative ions? ____positive_______________

•Do non-metals form positive or negative ions? ___________________________


•Do metals form positive or negative ions? ____positive_______________

•Do non-metals form positive or negative ions? ____negative_______________

Group 1A elements ie H, Li, Na, K, etc will form +1 ions.

Group 2A elements ie Be, Mg, Ca, Ba etc will form +2 ions.

Group 3A elements ie B, Al, Ga etc will form +3 ions.

Group 5A elements ie N, P, As etc will form –3 ions.

Group 6A elements ie O, S, Se etc will form –2 ions.

Group 7A elements ie F, Cl, Br, I etc will form –1 ions.

Group 8A elements never form ions.

With reference to the number of electrons that the noble gases have, can you explain why each of the above groups gain or lose a particular amount of electrons?

The other elements (the Transition metals, the Lanthanides metals and Actinide metals) can form more than one type of positive ion each. eg Sometimes chromium will lose two electrons and form a +2 ion. And sometimes chromium will lose three electrons and form a +3 ion. This could be confusing so chemists have decided to give a different name to each ion. If chromium loses two electrons the resulting ion (Cr+2) is called chromium II. And if chromium loses three electrons, then the resulting ion (Cr+3) is called chromium III.

For example:The charge on a copper I ion is +1.The charge on a copper II ion is +2.

What is the charge on each of the following ions?mercury II __________iron III __________iron II __________mercury I __________

For example:The charge on a copper I ion is +1.The charge on a copper II ion is +2.

What is the charge on each of the following ions?mercury II _____+2___iron III _____+3___iron II _____+2___mercury I _____+1___

Name each of the following ions:

(a) Cu+2 ______________________(b) Fe+3 ______________________(c) Cr+2 ______________________(d) Hg+2 ______________________


(a) Cu+2 __copper II ___________(b) Fe+3 __iron III ___________(c) Cr+2 __chromium II _________(d) Hg+2 __mercury II _________

Another naming convention that chemists use is for non-metal ions.

If a non-metal element forms an ion by gaining electrons we add –ide to the end of the non-metal’s name.

For example if a chorine atom gains one electron to form a –1 ion, Cl-1.

This ion is called the chloride ion.


(a) O-2 ______________________(b) S-2 ______________________(c) Br-1 ______________________(d) N-3 ______________________


(a) O-2 ___oxide ion _________(b) S-2 ___sulfide ion _________(c) Br-1 ___bromide ion _________(d) N-3 ___nitride ion _________

You are so

radical man!!

Sometimes when groups of atoms join together, then the whole group will gain or lose electrons. In the previous slide the potassium atom loses one electron to become a K+ ion.

The group of atoms (one manganese atom and four oxygen atoms) combine together and share this electron. This forms an ion known as a polyatomic ion (poly- means many) or a radical.

The radical in the previous example is known as the permanganate ion, and is written as MnO4

-1. You may have heard of other radicals eg carbonate (CO3

-2), bi-carbonate (HCO3-1),

hydroxide (OH-1), sulfate (SO4-2), etc.

Most of the radicals that we will look at this year are negative ions.

There is one positive radical we will encounter ie the ammonium ion (NH4+).