IONIC AND COVALENT BONDS

8th Grade Science

Case Study: The Hindenburg Myth Buster’s Mini Myth: http://dsc.discovery.com/tv-shows/mythbusters/videos/hindenburg-minimyth.htm

Blimps now use Helium instead of Hydrogen. Why?

Case Study: Hydrogen

What do you notice about Hydrogen?

Case Study: Hydrogen

Most abundant chemical substance Colorless, odorless, tasteless, non-toxic,

highly combustible gas Very high chemical reaction

Why? It only has one valence electron Readily combines and forms Covalent Bonds

Case Study: Noble Gases

What do you notice about the Noble Gases?

Case Study: Noble Gases

He, Ne, Ar, Kr, Xe, Rn Odorless, colorless, gases Very low chemical reactivity

Why? Their outer shell of valence electrons are

considered “full” Gives little tendency to participate in chemical

reactions

Case Study Conclusion

Stable-Atoms are “happy” when they have full energy levels.

Having an uneven amount of valence electrons causes atoms to react with one another.

Octet Rule: atoms will combine with each other in order to have eight valence electrons like a noble gas.

Ions

What compound is being pictured ?

Ions

Infer what has happened in these diagrams:

Review: Ions

Ions have a charge Cation: loses an electron

Positive charge Anion: gains an electron

Negative charge

Which element is a cation? Which is an Anion?

Ionic Bonds- Loss or Gain

Ionic Bonds: the bonds that hold ions together

Compound: a pure substance containing two or more elements

Ionic Bonds- Loss or Gain

Infer what has happened in this picture

Ionic Bonds- Loss or Gain

Infer what has happened in this picture

Compounds can be created many ways by losing more then one electron or gaining more then one electron.

Covalent Bonds- Sharing

Certain atoms cannot lose or gain electrons, because it is to difficult and takes so much energy.

Covalent Bonds- Sharing

Covalent Bond- the chemical bond that forms between nonmetal atoms when they share electrons

The shared electrons are attracted to the nuclei of both atoms

Covalently bonded compounds are called molecule compounds.

Molecule: a neutral particle formed when atoms share electrons

Covalent Bonds- Sharing

Why aren’t ions being formed?

Covalent Bonds- Sharing

Double Bond: when two pairs of electrons are shared

Triple Bond: when three pairs of electrons are shared

Periodic Table Trend

• Covalent Bond is when two non-metals bond together.

• Ionic Bond is when a metal and a non-metal bond together.

Covalent Bonds- Sharing

Double Bond: when two pairs of electrons are shared

Triple Bond: when three pairs of electrons are shared

Chemical Formulas

Chemicals are represented by letters Some symbols are the first letter of their name Some symbols are the first letters of their name

in another language Potassium is K, in latin potassium is kalium

Compounds are shown using symbols and numbers the subscript illustrates how many atoms are in the

molecule Chemical formula:

a mathematical sequence that expresses a chemical reaction

Combination of chemical symbols and numbers that show which elements are present in a compound