Molecules and Ions

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Slide 1

Molecules and Ions

Image courtesy of www.lab-initio.com

Slide 2

Molecules

Two or more atoms of the same or different elements, covalently bonded together.

Molecules are discrete structures, and their formulas represent each atom present in the molecule.

Pentane, C5H12

Slide 3

Covalent Network Substances

Covalent network substances have covalently bonded atoms, but do not have discrete formulas.

Why Not??

Graphene – carbon allotrope

Slide 4

Ions

Cation: A positive ion

Mg2+, NH4+

Anion: A negative ion

Cl-, SO42-

Ionic Bonding: Force of attraction between oppositely charged ions.

Ionic compounds form crystals, so their formulas are written empirically (lowest whole number ratio of ions).

Slide 5

Predicting Ionic Charges

Group 1: Lose 1 electron to form 1+ ions

H+

Li+

Na+

K+

Rb+

Cs+

Slide 6

Predicting Ionic Charges

Group 2: Loses 2 electrons to form 2+ ions

Be2+

Mg2+

Ca2+

Sr2+

Ba2+

Slide 7

Predicting Ionic Charges

Group 13: Loses 3

electrons to form

3+ ions

B3+

Al3+

Ga3+

Slide 8

Predicting Ionic Charges

Group 14:

Loses 4

electrons or gains

4 electrons

Caution! C22- and C4- are both called carbide

Slide 9

Predicting Ionic Charges

Group 15:

Gains 3

electrons to form

3- ions

N3-

P3-

As3-

Nitride

Phosphide

Arsenide

Slide 10

Predicting Ionic Charges

Group 16: Gains 2

electrons to form

2- ions

O2-

S2-

Se2-

Oxide

Sulfide

Selenide

Slide 11

Predicting Ionic Charges

Group 17: Gains 1

electron to form

1- ions

F1-

Cl1-

Br1-

Fluoride

Chloride

Bromide

I1-

Iodide

Slide 12

Predicting Ionic Charges

Group 18: Stable Noble gases do not form ions!