Combining ElementsHow Chemical Compounds Are Made

Combining Elements

• Elements can exist on their own but most matter consists of two or more elements combined together

• How do they combine??

Metals and Non-metals

• Metals have a tendency to lose electrons and form positive (+) ions.

• Non-metals tend to gain electrons and form negative (-) ions

• Positive and negative charges attract• When a positive ion and a negative ion bind

together they form an ionic bond

Example (Sodium and Fluorine)

• An atom of Sodium has a single electron in its outer orbittal. This makes it unstable

• An atom of fluorine has seven electrons in its outer orbital. It needs one more to be stable.

Metal and Non-Metal

• So they make a deal!

• The sodium gives an electron to fluorine

• Now they’re both happy

• The only thing is:– They’re not atoms any more

•They’re IONS• An ion is like an atom but it has a charge

• Now REMEMBER–Opposites attract!

Ionic Compounds

• So sodium and fluorine are attracted to each other and form an inseparable bond

And they call themselves Sodium Fluoride!! (or NaF)

Sodium Fluoride is an Ionic Compound

Ionic Compounds

Here’s another example:• Let’s take Calcium and Chlorine

• Calcium needs to get rid of two electrons to be stable but Chlorine only needs one.

• SO WHAT CAN THEY DO?

Building Ionic Compounds

• What if Chlorine found a friend?

• Another chlorine atom!

Making Ionic Compounds

• Now Calcium can give one electron to each of them!

• Now everyone’s happy!

Making Ionic Compounds

• This compound is called Calcium Chloride• Or CaCl2

• Because there is one calcium ion and two chlorine atoms

Making Ionic Compounds

• Making ionic compounds is easy if you follow a few rules

1. Write down the name (or symbol) of each element starting with the metale.g. Potassium (K) Sulfur (S)

2. Beside each one, write down the number of electrons that the element needs (or has to give away) to be stable

K (1) S (2)3. Now criss cross the numbers

K (1) S (2)

Making Ionic Compounds

• This gives us K2S or Potassium Sulfide• Try these

Metal Non-metal Metal Symbol &

Electrons to lose

Non-metal Element

and Electrons to

gain

Final Formula

(Criss cross)

Magnesium Nitrogen Mg (2) N (3) Mg3N2

Lithium Chlorine

Calcium Carbon

Aluminum Silicon

• One last thing– If you can divide both numbers by a highest common

factor: DO IT!!

–Example: Calcium OxideCa2O4

• 2 and 4 are both divisible by 2 so• Ca2O4 becomes CaO2

Naming Binary Ionic Compounds

• A binary ionic compound is an ionic compound with two elements.

• They’re very easy to name.1. Write down the metal first, then the non-metal.2. The metal keeps its name. 3. Now take the non-metal, write down its first

syllable and then write ide. 4. That’s it! You’re done!

Naming Binary Ionic Compounds• Example

•Mg3P2

•Magnesium PhosphideNow try these

Formula NameNa2OAlCl3

Be3S2

More PracticeTry these (Name Formula)

Compound Symbols and “Criss-Cross”

Formula

Calcium Chloride

Beryllium Phosphide

Aluminum Oxide

Potassium Nitride

Magnesium Carbide

Sodium Iodide

Lithium Sulfide

Now Try These (Formula Name)

Formula NameCaF2

Al4Si3

Mg3P2

BeI2

LiFCa2CNa3P