Combining Elements How Chemical Compounds Are Made Combining

Combining Elements How 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

What makes an Atom Stable? • First of all, what does “stable” even mean? – Answer: A stable atom is one that will stay the way it is. It will not gain or lose any of its components (protons, neutrons or electrons) • Atoms are stable if their outer orbital is full of electrons!

What Makes An Atom Stable? Example – Helium An atom of Helium only has one orbital and this orbittal has two electrons. Since the first orbital can only hold two electrons, the orbital is full. That means that helium is stable.

Unstable Atoms • Example: Sodium has 11 electrons; 2 in the first orbital, 8 in the second and 1 in the third. It’s outer orbital is not full since it only has one electron. So How Can It Become Stable? The easiest way for it to become stable is for the one electron to leave.

Making an Unstable Atom Stable • If Sodium loses an electron it will be stable (and happy !!!) Just one problem If an atom does not have The same number of protons and electrons then it is not an atom

Making an Atom Stable • But this isn’t really a problem All we have to do is change its name. So we don’t call it an atom Anymore. We call it an Ion! An ion is an atom that has gained or lost electrons. Since Sodium has lost an electron (which is negative) it becomes a positive ion

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 Na. F) 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 Ca. Cl 2 • 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 metal e. 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 • Try these Metal Non-metal Magnesium Nitrogen Lithium Chlorine Calcium Carbon Aluminum Silicon K 2 S or Potassium Sulfide Metal Non-metal Final Symbol & Element Formula Electrons to and (Criss cross) lose Electrons to gain Mg (2) N (3) Mg 3 N 2

• One last thing – If you can divide both numbers by a highest common factor: DO IT!! – Example: Calcium Oxide Ca 2 O 2 • 2 and 2 are both divisible by 2 so • Ca 2 O 4 becomes Ca. O

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 • Mg 3 P 2 • Magnesium Phosphide Now try these Formula Na 2 O Al. Cl 3 Be 3 S 2 Name

More Practice Try these (Name Compound Calcium Chloride Beryllium Phosphide Aluminum Oxide Potassium Nitride Magnesium Carbide Sodium Iodide Lithium Sulfide Formula) Symbols and “Criss. Cross” Formula

Now Try These (Formula Ca. F 2 Al 4 Si 3 Mg 3 P 2 Be. I 2 Li. F Ca 2 C Na 3 P Name) Name