Chapter 8 Covalent Bonding

Section 8.1 Molecular compounds: New Vocab Covalent bond: atoms held together by sharing electrons

How is a covalent bond different from ionic bonds?

Molecule A group of neutral atoms held together by covalent bonds.

Diatomic molecule A molecule consisting of two atoms of the same element.

Diatomic molecules: Hi, bronclif! HI BrONClF Hydrogen, Iodine, Bromine, Oxygen, Nitrogen, Chlorine, Fluorine

Oxygen is a diatomic molecule-it has two O atoms bound together covalently

Why do some elements form diatomic molecules and others don’t? The octet rule! ( Use N2 )

Neon has 8 valence electrons Neon has 8 valence electrons. It doesn’t need to form bonds with other atoms to become stable!

Molecular compound Atoms form molecules, and molecules bind together to form compounds. A molecular compound is a compound made of molecules!

4 differences between ionic and molecular compounds: (examples follow) Terminology Spatial orientation Melting points & boiling points Composition

1. Terminology: formula unit vs. molecule 2. Orientation: crystal vs 1.Terminology: formula unit vs. molecule 2.Orientation: crystal vs. no crystal

3. Molecular compounds have lower melting points and boiling points than ionic compounds!

4. Composition Molecular compounds are made of two non metals Ionic compounds are made of a metal and a non-metal (cobalt chloride crystals)

Molecular Formula Is the chemical formula It shows how many atoms of each element a molecule contains. The subscript after each symbol tells you the number of atoms of that element is found in the molecule. C6H12O6 : How many atoms of each element are contained in this sugar?

More about molecular formulas: If there is one atom of an element in a molecule, the subscript “1” is omitted. H2O: A molecule of water has only 1 oxygen atom—the subscript is left out. Subscripts are NOT always the lowest whole number ratios. Does NOT tell you the molecule’s structure.

Different types of models: NH3 = ammonia’s molecular formula