Unit 9 Chapter 6 – Chemical Bonds

Essential Questions 1)What is the difference between compounds and mixtures? 2)Explain the difference between an ion and molecule 3)Differentiate between an ionic/ covalent/ polyatomic compound? Explain the role of bonding in them.

4)What is the difference between a binary compound and a polyatomic compound? 5)What are the rules to be followed when naming a compound or writing its formula?

Some elements combine chemically and no longer have the same properties they did before forming a compound. Atoms form compounds when the compound is more stable than the separate atoms.

Stability in Bonding  Noble gases are more chemically stable than other elements because they have a complete outer energy level.  Elements that do not have full outer energy levels are more stable in compounds.

Atoms can lose, gain, or share electrons to get a stable outer energy level. A chemical bond is the force that holds atoms together in a compound.

Bonds Atoms bond when their valence electrons interact. Remember – everyone wants to be happy like the noble gases.

Lewis Dot Diagrams Shows each valence electron as a single dot. Examples: Sodium Carbon Fluorine

Connecting the dots You can show how the two elements will combine using the dots. Cl

There are three types of atomic bonds: –Ionic –Covalent –Metallic I did not say atomic bombs

Bonds ionic bonds –Between a metal and a non-metal. – The metal loses it’s electrons and the non-metal takes the electron from the metal.

Ionic Bonds

Bonds cont. covalent bonds –Two non-metals –The two non- metals share electrons.

bonds cont. metallic bonds – positively charged metal ions are surrounded by a cloud of electrons, the outer energy level held loosely so the electrons can flow easily between the ions. These metals conduct electricity because the outer electrons can easily move around.

Ionic Bonds When an atom gains or loses an electron it becomes charged (no longer neutral) this is called ionization. An ion is a charged atom.

oppositely charged ions –Metals become positively charged when they give away valence electrons –Non-metals become negatively charged when they gain valence electrons.

Cation Positive ion Made when an atom loses an electron. Anion Negative ion Made when an atom gains an electron. Protons = 3 Electrons = 3 2 Protons = 9 Electrons = 910

Covalent Bonds Formed between two non- metals. Is the sharing of electrons –Neither atom gives up valence electrons, they share them.

Covalent bonds form molecules. Atoms may share more than one pair of electrons. Atoms do not always share electrons equally. Polar and non-polar molecules

Polyatomic Ions Compounds with both ionic and covalent bonds. Acts the same as any other ion.

Polyatomic Ions Examples: –Ammonium NH 4 + –Hydroxide OH - –Sulfate SO 4 +2 –Carbonate CO 3 -2 Calcium Carbonate CaCO 3

Naming Binary Compounds