Chemical Formulas & Naming. What We Already Know O We have talked about pure substance being broken down into elements and compounds --more than one element.

Chemical Formulas &

Naming

What We Already KnowO We have talked about pure

substance being broken down into elements and compounds

--more than one element combined is a compound

O We have talked about how to figure out the number of valence electrons an element has

O So, how do these things relate to forming a compound…why do the elements even want to hang out together?

CompoundsA chemical formula tells us both the elements involved and how many of

each are necessaryAlBr3

In this case, one Aluminum and 3 bromine are present

If there is only one of something present then no subscript is used

How many atoms are present in these compounds?

O NaHCO3

O H2SO4

O KNO3

Here’s a tricky one…O Mg(OH)2

Mg(OH)2

In this case there is a hydroxide ion present (OH) and everything that is

inside the parenthesis has to multiplied by what is outside the

parenthesis

Let’s try another one…

Mg(NO3)2

There is one MgThere are two NThere are 6 O

Octet RuleO Atoms tend to want to

achieve the electron configuration of a noble gas which has eight electrons in is highest occupied energy level

O Atoms are willing to gain or lose an e- to achieve this

O Gaining or losing an e- causes the atom to then be a charged particle.

IonsAn atom with no charge has an equal

number of protons and electronsSo what about atoms with a charge?

Its called an ionO Cation- A positively charged ion formed

by an atom’s loss of a valence electron.Example Na+

O Anion- A negatively charged ion produced by an atom gaining an electron.

Example Cl-

Ions ContinuedO Monatomic ions is one element with

a charge

O Polyatomic ions is more than one element with a charge

Example: SO42-

Which Elements Will Gain and

Which Will Lose Electron

Combining ElementsIt is the tendency to lose or to gain electrons

that determine why elements combine a certain way

Although ions carry a charge they have to combine in such a way that their charge

cancels out.

Na+ Cl-

Sodium wants to lose an electron and Chlorine is more than happy to accept that electron

The 5 Steps for writing anionic compound formula:

1. Write the symbols of the two elements.

2. Write the valence of each as superscripts.

3. Drop the positive and negative signs.

4. Crisscross the superscripts so they become subscripts.

5. Reduce when possible.

Formula for boron oxide

1.Write the symbols of the two elements.

B O

Formula for boron oxide

2. Write the valence for each element

B3+ O2-

Formula for boron oxide

3. Drop the positive & negative sign.

B3 O2

Formula for boron oxide

4. Crisscross the superscripts so they become subscripts.

B3 O2

Formula for boron oxide

5. Reduce subscripts when possible.(not possible here)

B2O3

Examples of Reductionof Subscripts:

Sr 2O2 SrO

Al3P3 AlP

Pb2O4 PbO2

Subscripts can only be reduced if they are divisible by the same

number

Reduces to

Reduces to

Reduces to

Naming Ionic Compounds (Regular & Polyatomic)

1. Write the name of the cation (metal)

2. Write the name if the anion (nonmetal)

-If only 2 elements, cut off the ending of the 2nd element and add “ide”

-If a polyatomic ion, use the name the class copy data sheet gives you.

Examples

1. NaCl

2. MgSO4

3. K3PO4

4. Ca(ClO3)2

5. NH4NO2

O Sodium chloride

O Magnesium sulfate

O Potassium phosphate

O Calcium chlorate

O Ammonium nitrite

Naming Ionic Compounds (Variable Charge)

1. Check to see that these metal are in the d-block and have a variable charge

2. Write the name of the cation (metal) with (roman numerals which indicates charge)

3. Write the name of the anion (nonmetal or polyatomic ion)

4. The anion is named by adding –ide to the root of the element name

Examples:O Lead (IV) OxideO Iron (II) sulfateO Cobalt (II)

chlorideO Copper (II)

phosphateO Zinc chloride

O PbO2

O FeSO4

O CoCl2O Cu3(PO4)2

O ZnCl2