23
Init 10/28/2010 by Daniel R. Barnes

Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Embed Size (px)

Citation preview

Page 1: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Init 10/28/2010 by Daniel R. Barnes

Page 2: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+

Cl-

Na+

Cl-

Na+

Cl-

Na+

Cl-

Page 3: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na
Page 4: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+

Cl-

Na+

Cl-

Na+

Cl-

Na+

Cl-

Page 5: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Ionic compounds typically consist of a metal and a nonmetal.

IONIC COMPOUND RE-CAP

Nonmetals generally have much higher electronegativities than metals, so the nonmetal will steal electrons from the metal.

+

Page 6: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Ionic compounds typically consist of a metal and a nonmetal.

IONIC COMPOUND RE-CAP

Nonmetals generally have much higher electronegativities than metals, so the nonmetal will steal electrons from the metal.

As a result, the nonmetal atom becomes a negatively-charged ion, and the metal atom becomes a positively-charged ion.

Because they are now oppositely-charged, the negative nonmetal ion and the positive metal ion are attracted to each other.

This electrostaic attraction constitutes an ionic bond between the metal ion and nonmetal ion.

Because of their attraction for each other, the positive metal ions and the negative nonmetal ions will form an orderly crystal structure.

+

Page 7: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Although ionic compounds, like salt, are made of positive ions and negative ions, the amount of positive charge always equals the amount of negative charge.

Even though it’s made of plusses and minuses, an ionic compound, overall, is neutral.

Each ion in an ionic compound will have an electrical charge that depends upon its location on the periodic table.

IONIC COMPOUND RE-CAP

Page 8: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Please note the numbers at the tops of the columns.

The ones that matter are the ones with the letter “A” after themThese numbers tell you . . .

. . . how many valence electrons each element has.

This number is super-important, because it tells you how many electrons the atom is going to lose or gain.Remember that atoms like to either completely empty or completely fill their outer valence shells.

How many electrons an atom loses or gains determines the atom’s electric charge when it becomes an ion.

Page 9: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na
Page 10: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES1. What is the chemical formula of sodium chloride?

Step one: determine the symbol and charge of each ion.

Sodium = Na = from group 1A loses 1 e- Na+

Sodium has one valence electron, so it has two options.

It can lose the electron to empty its valence shell, orit can gain seven more electrons to fill its valence shell.

Since losing one electron involves fewer electrons than gaining seven, sodium loses one electron.

Remember that because electrons are negative, losing electrons makes an atom positive.

Page 11: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES1. What is the chemical formula of sodium chloride?

Sodium = Na = from group 1A loses 1 e- Na+

Chlorine = Cl = from group 7A gains 1 e- Cl-

Chlorine has seven valence electrons, so it has two options.

It can lose all seven valence electrons to empty its valence shell, or it can gain one extra electron to fill its valence shell.

Since gaining one electron involves fewer electrons than losing seven, chlorine gains one electron.

Remember that because electrons are negative, gaining electrons makes an atom negative.

Now we know the symbols and the charges of the two ions in sodium chloride.

Page 12: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES1. What is the chemical formula of sodium chloride?

Sodium = Na = from group 1A loses 1 e- Na+

Chlorine = Cl = from group 7A gains 1 e- Cl-

Now, we need to figure out how many of each ion will make a single formula unit of the compound.

We need to make sure that the number of plusses equals the number of minuses.

This one is easy because the sodium ion is plus one and the chlorine ion is minus one.

The two ions are electrically equal but opposite, so one of each ion will be fine.

Na Cl

Page 13: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES2. What is the chemical formula of beryllium chloride?

Beryllium = Be = from group 2A loses 2 e- Be2+

Chlorine = Cl = from group 7A gains 1 e- Cl-

Be2+ Cl-

Now, we need to figure out how many of each ion will make a single formula unit of the compound.

Beryllium chloride is going to be a little more complicated than sodium chloride because there are two plusses but only one minus.

The solution is pretty simple, though. Just add another chloride ion, and you’ve got a total of two minuses.

Cl-

+2 -2’s:

BeCl2

Page 14: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES3. What is the chemical formula of potassium oxide?

Potassium = K = from group 1A loses 1 e- K+

Oxygen = O = from group 6A gains 2 e- O2-

K+ O2-

Potassium oxide has a problem similar to beryllium chloride, but this time, there’s more minus than plus.

+2 -2’s:

K2OK+

A neutral oxygen atom is hungry for two electrons, but a potassium atom is only going to give up one. It’s going to take two potassium ions to balance out against a single oxide ion.

Remember that ionic compounds form when nonmetals steal electrons from metals.

Page 15: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES4. What is the formula of aluminum oxide?

Aluminum = Al = from group 3A loses 3 e- Al3+

Oxygen = O = from group 6A gains 2 e- O2-

Al3+ O2-

With aluminum oxide, the plusses don’t equal the minuses either.

At first, there are 3 plusses but only 2 minuses, so what we need is more minuses. We get this by adding another oxide ion.

Unfortunately, there is now a total of 4 minuses, which is too much. We need another aluminum ion.

This one’s going to be a bit trickier to balance. There are two ways to go about it. We’ll do the “one ion at a time” method first.

O2-Al3+

Page 16: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES4. What is the formula of aluminum oxide?

Aluminum = Al = from group 3A loses 3 e- Al3+

Oxygen = O = from group 6A gains 2 e- O2-

Al3+ O2-

Oh boy. Now we have more plusses than minuses again.

+6 -6’s:

Al2O3O2-Al3+

One more oxide ion should help.

O2-

Holy cow! I think it’s balanced now! Yay for correct answers! Yay!

(There is a quicker way than this, though, called the “criss-cross” method. We’ll show it to you a little later.)

Page 17: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES5. What is the formula of iron (III) bromide?

Iron = Fe if (III) loses 3 e- Fe3+

Bromine = Br = from group 7A gains 1 e- Br -

Fe3+ Br -

The “(III)” means that the iron is in the +3 “oxidation state”.

+3 -3’s:

FeBr3

For now, consider Roman numerals to indicate positive charge.

Now, we have the usual problem of getting plusses equal to minuses. Keep adding ions until + = - .

Br -

Br -

Page 18: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES6. What is the formula of iron (II) nitride?

Iron = Fe if (II) loses 2 e- Fe2+

Nitrogen = N = from group 5A gains 3 e- N3-

Fe2+ N3-

Last time, it was iron (III), and now it’s iron (II). As it turns out, iron has more than one possible oxidation state. That’s true of a lot of elements.

+6 -6’s:

Fe3N2N3-Fe2+

Fe2+

Once again, though, the Roman numeral tells you . . . . . . the positive charge of the metal ion.

Page 19: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Sodium chloride is made of the ions Na+ & Cl- The formula of sodium chloride is NaCl

Beryllium chloride is made of the ions Be2+ & Cl- The formula of beryllium chloride is BeCl2

Potassium oxide is made of the ions K+ & O2- The formula of potassium oxide is K2O

Aluminum oxide is made of the ions Al3+ & O2- The formula of aluminum oxide is Al2O3

Iron (III) bromide is made of the ions Fe3+ & Br - The formula of iron (III) bromide is FeBr3

Iron (II) nitride is made of the ions Fe2+ & N3- The formula of iron (II) nitride is Fe3N2

DO YOUSEE APATTERN?

Page 20: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Sodium chloride is made of the ions Na+ & Cl- The formula of sodium chloride is NaCl

Beryllium chloride is made of the ions Be2+ & Cl- The formula of beryllium chloride is BeCl2

Potassium oxide is made of the ions K+ & O2- The formula of potassium oxide is K2O

Aluminum oxide is made of the ions Al3+ & O2- The formula of aluminum oxide is Al2O3

Iron (III) bromide is made of the ions Fe3+ & Br - The formula of iron (III) bromide is FeBr3

Iron (II) nitride is made of the ions Fe2+ & N3- The formula of iron (II) nitride is Fe3N2

The “Criss-Cross” short cut usually works just fine.

Usually . . .

Page 21: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

BINARY IONIC COMPOUND EXAMPLES7. What is the formula of tin (IV) oxide?

Tin = Sn if (IV) loses 4 e- Sn4+

Oxygen = O = from group 6A gains 2 e- O2-

Sn4+ O2-

The one-ion-at-a-time method gives us . . .

+4 -4’s:

SnO2O2-

The criss-cross method gives us . . . Sn4+ O2-

Sn2O4If you do the criss-cross method and you get subscripts that all can be divided by the same number, you should divide them all by the same number.

Since you can divide both two and four by two, do so, and you get our original answer.

Page 22: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

2

4=

1

2

In math, if you get 2/4 as your answer, you’re supposed to . . .

. . . reduce the fraction to . . .

You do this by dividing the top and bottom of the fraction by the same number. (In this case, dividing the top and the bottom by two)

If, in chemistry, you get . . . Sn2O4

You should reduce it to . . .

SnO2

Remember this if you decide to use the “criss-cross” method instead of the “one ion at a time” method.

Page 23: Init 10/28/2010 by Daniel R. Barnes Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na + Cl - Na

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+ Cl-

Na+Cl-

Na+

Cl-

Na+

Cl-

Na+

Cl-

Na+

Cl-

A salt crystal may go on and on, but this presentation is over.