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Inter-molecular forces

Inter-molecular forces

Works based on

Molecular Geometry

Molecular Geometry

Bonding types & Structures

Bonding types & Structures

Determined by

Determined by

Types of Bonds

Why atoms bond

Atoms are most stable when their outer shell of electrons is full

Atoms bonds to fill this outer shellFor most atoms, this means having 8

electrons in their valence shellCalled the Octet Rule

Common exceptions are Hydrogen and Helium which can only hold 2 electrons.

One way valence shells become full

Na-

-

- --

-

-- - -

Cl-

-

- --

-

-- - -

-

-

-

--

-

-

Sodium has 1 electron in it’s valence shell

Chlorine has 7 electrons in it’s valence shell

Some atoms give electrons away to reveal a full level underneath.

Some atoms gain electrons to fill their current valence shell.

-

One way valence shells become full

Na-

-

- --

-

-- - -

Cl-

-

- --

-

-- - -

-

-

-

--

-

-

-+ -

The sodium now is a cation (positive charge) and the chlorine is now an anion (negative charge).

These opposite charges are now attracted, which is an ionic bond.

Ionic Bonding—Metal + Non-metal

Metals tend to lose their electrons and non-metals gain electrons

Metals become cations (positively charged)Non-metals become anions (negatively charged)The cation & anion are attracted because of

their charges—forming an ionic bond

Bonding between non-metals

When two non-metals bond, they share electrons

Non-metals that share electrons evenly form non-polar covalent bonds

Non-metals that share electrons un-evenly form polar covalent bonds

Metals bonding

Metals form a pool of electrons that they share together.

The electrons are free to move throughout the structure—like a sea of electrons

Atoms aren’t bonded to specific other atoms, but rather to the network as a whole

Type of bond

Electrons Melting/ Boiling Point

Solubility

Electricity Example

Ionic

Polar Covalent

Non-Polar Covalent

Metal

Bond type affects properties

The type of bonding affects the properties of the substance.

There are always exceptions to these generalizations (especially for very small or very big molecules), but overall the pattern is correct

Melting/Boiling Points

Ionic bonds tend to have very high melting/boiling points as it’s hard to pull apart those electrostatic attractionsThey’re found as solids under normal conditions

Polar covalent bonds have the next highest melting/boiling pointsMost are solids or liquids under normal conditions

Non-polar covalent bonds have lower melting/boiling pointsMost are found as liquids or gases

Solubility in Water

Ionic & polar covalent compounds tend to be soluble in water

Non-polar & metallic compounds tend to be insoluble

Conductivity of Electricity

In order to conduct electricity, charge must be able to move or flow

Metallic bonds have free-moving electrons—they can conduct electricity in solid and liquid state

Ionic bonds have free-floating ions when dissolved in water or in liquid form that allow them conduct electricity

Covalent bonds never have charges free to move and therefore cannot conduct electricity in any situation

Copy this table

Type of bond

Electrons Melting/ Boiling Point

Solubility

Electricity Example

Ionic Transferred from Cation to Anion

High: Hard to pull electrostatic attractions

High High when in water or in a liquid

Any type of Salt

Polar Covalent

Share Electrons unevenly

High High Poor Water

Non-Polar Covalent

Share Electrons Equally

Low Insoluble Poor Methane Gas

Metal Sea of Electrons

Depends on metals

Insoluble Excellent Bronze (Iron and Copper Alloy)