Ions

Chemistry 1

What are they?

Ions are charged atoms (or groups of atoms)

Have either gained or lost electrons

Characteristics of Ions

•Conduct electricity

•Like charges repel

•Opposite charges attract

Electrical Conductivity

Metals conduct electricity because the electrons are held loosely by each atom. When an electron is added to one end, another electron will be bumped off the opposite end.

e- e-e- e-e- e- e- e- e- e- e- e- e-e- e-

Electrical Conductivity

Ionic compound Dissolved in water

Ionic compounds can conduct electricity ONLY when the ions are free to move about. (i.e. They must be either melted or dissolved.)

Why are they charged?

•Atoms have both p+ and e-. If these are present in equal numbers the +/- charges will balance out.•If they are in unequal numbers the result is an ion

e.g. Na

+ 1 e-11p+

11e-

11p+

10e-

Na+

Why are they charged?

e.g. Mg

+ 2 e-12p+

12e-

12p+

10e-

Mg2+

Why are they charged?

e.g. F

+ 1 e-9p+

9e-

9p+

10e-

F-

Keep your hands off the nucleus!!

You are NOT allowed to move protons, only electrons

You don’t know where it’s been.

One word of Caution:

NomenclatureCation: a positive ion

Has lost 1 or more e-

C, a + ion.

Anion: a negative ionHas gained 1 or more e-

A Negative Ion

Insert your owncute picture here

(the cat’s eyes are + signs)

Cations: Metals – lost electron(s)Name is the same as the name of the atom.

e.g.

K = potassium K+ = potassium (ion)

Na = sodium Na+ = sodium (ion)

Mg = magnesium Mg2+ = magnesium (ion)

Ca = calcium Ca2+ = calcium (ion)

Nomenclature - cations

Anions: Non-metals – gained electron(s)Name is the same as the name of the atom

w/ the ending changed to “-ide”.e.g.

Cl = chlorine Cl- = chloride

F = fluorine F- = fluoride

N = nitrogen N3- = nitride

O = oxygen O2- = oxide

Nomenclature - anions

Predicting Charges

•Noble gases are inherently stable.•Electrons are responsible for chemical reactivity.•Might guess that the number of electrons on Noble gases must be very stable.

Assume that atoms will either gain or lose electrons to end up with the same number of electrons as the nearest Noble gas

Predicting Charges - huh?

Find the element on the periodic table - what is its atomic number?

Find the nearest Noble gas (Nobel gases are the elements in the far right column. The nearest will have an atomic number closest to the element you’re trying to predict)

Calculate how many electrons must be added or removed.

Predicting Charges - practicePredict the charge on an ion formed by Iodine (I)

What’s the nearest Noble gas?

What’s Iodine’s atomic number?

Does I need to gain or lose e- to have the same number of e-’s as Xenon? How many?

So what’s the charge?

53

Xenon (Xe)

Gain 1 electron

1- (or -1 is okay)

Predicting Charges - practicePredict the charge on an ion formed by Bromine (Br)

What’s the nearest Noble gas?

What’s bromine’s atomic number?

Does Br need to gain or lose e- to have the same number of e-’s as Krypton? How many?

So what’s the charge?

35

Krypton (Kr)

Gain 1 electron

1- (or -1 is okay)

Predicting Charges - practicePredict the charge on an ion formed by Sulfur (S)

What’s the nearest Noble gas?

What’s sulfur’s atomic number?

Does S need to gain or lose e-’s to have the same number of e-’s as Argon? How many?

So what’s the charge?

16

Argon (Ar)

Gain 2 electrons

2- (or -2 is okay)

Predicting Charges - practicePredict the charge on an ion formed by Potassium (K)

What’s the nearest Noble gas?

What’s potassium’s atomic number?

Does K need to gain or lose e-’s to have the same number of e-’s as Argon? How many?

So what’s the charge?

19

Argon (Ar)

Lose 1 electron

1+ (or +1 is okay)