Unit: Chemical Bonding:
Charged things interact with other charged things
If the charges are opposite (protons and electrons), things attract.
Three types of bonds: Metallic, Ionic and Covalent
I. 17.1- Metals and Alloys:
a. Ion-an atom that has either lost or gained one or more electrons
b. Metallic Bond: a fluid of electrons holds the positively charged metal ions together
c. Alloy- any mixture composed of two or more metallic elements
d. Ex:
i. Steel- Iron, Manganese and Carbon
ii. Brass- Copper and Zinc
II. 17.2 Ionic Bonds: The attraction between two oppositely charged ions
III. 17.3 Covalent Bonds: 2 elements share valence electrons (co-sharing and valent-valence electrons)
a. Molecule- the smallest particle of a substance that retains all the properties of the substance and
is composed of one or more atoms
IV. 17.4- Covalent Polarity:
a. Dipole- one side of a molecule is slightly positive and one side is slightly negative (di-2 poles)
b. Electronegativity- how well atoms are able to pull elections toward themselves
c. Ex:
i. H and F, Fluorine is more electronegative and holds electrons closer and therefore that
side of the molecule is slightly negative.
d. Nonpolar: no dipole is formed (H2)
e. Polar: Electronegativities are not equal
V. 17.5- Molecular Polarity:
a. Great Analogy- Chemical bonding is like a tug of war. Each atom is pulling on electrons.
When one atom pulls harder than the other the result is a polar molecule.
i. People = Atoms,
ii. Rope = electrons,
iii. Strength of people = electronegativity
b. Ex: H2O, Oxygen is more electronegative that hydrogen and therefore “tugs” on electrons harder.
i. This ends up forming a polar molecule
ii. The oxygen side is slightly negative
iii. The hydrogen side is slightly positive
c. Polar molecules attract one another creating substances with higher boiling points.
i. Ex:
1. Nitrogen is nonpolar and boils at –196oC
2. Water is polar and boils at 100oC