8th grade ch 1 sec 4 covalent bonds

Ch. 1 Sec. 4

ss

covalent bonds

• usually form between 2 nonmetals

C2H6

molecule •neutral group of atoms joined by covalent bonds

CH4

Carbon has 4 electrons in its outer shell. It needs 4 more electrons.

Hydrogen needs 1.

Nonpolar bond• covalent bond in which valence

electrons are shared equally

• ex: oil

Polar bond

Covalent bond in which electrons are shared unequally

Water molecules are polar

Polar bond

Polar bond

Unequal sharing of electrons

Polar bond

• Unequal sharing of an electron in a polar-covalent bond between 2 atoms is like 2 neighbors buying and sharing one snowblower.

• But one neighbor has a much

longer driveway than the other. • After a snowstorm, the snowblower will

spend much more of its time at the house with the longer driveway than the other.

• F, O, Cl have long driveways.

Be Nice, Clear Your IceBe Nice, Clear Your Ice

Fluorine forms a nonpolar bond with

another fluorine atom.

In hydrogen fluoride, fluorine attracts

electrons more strongly than hydrogen does, so

the bond formed is polar.

DOUBLE BOND

• 2 pairs of electrons are shared

TRIPLE BOND

• 3 pairs of electrons are shared

molecular compound

• molecules having covalently bonded atoms

H2O

Properties of molecular compounds

CH3CH2OH

1. Lower point

& boiling point

2. Poor conductors of electricity

Click here for Ionic and Covalent Bonding Quiz

Review Time

What holds covalently bonded atoms together?

• The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.

How does unequal sharing of electrons occur, and how does it affect molecules?

• Atoms of some elements pull more strongly on shared electrons than do atoms of other elements. As a result, the electrons are pulled more toward one atom, causing the bonded atoms to have slight electrical charges.

What are the properties of molecular compounds?

• Molecular compounds generally have lower melting points and boiling points, and they do not conduct electricity when dissolved in water.