CHEMICAL BONDS

CHEMICAL BONDING I

Constructing Molecular Models

What limited the number of “atoms” you could connect?

Black – 4, Red – 2, White - 1

Energy levels (valence levels)

Level 1: ___ electrons

Level 2: ___ electrons

Level 3: ___ electrons

This energy level can hold __ more electrons

Level 1Level 2

How many more electrons can this atom hold? ______

Is it easier to lose 1 electron, or gain 7?

The third level can hold up to 18 electrons.

What is happening here?

The Na atom is ________________ an electron and the Cl atom is ______________ an electron.

The Na atom becomes _______ charged, the Cl atom becomes _____ charged.

They are attracted to each other and form a bond.

• Atoms whose shells are not full tend to interact with other atoms and gain, lose, or share electrons

HYDROGEN (H)Atomic number = 1

CARBON (C)Atomic number = 6

NITROGEN (N)Atomic number = 7

OXYGEN (O)Atomic number = 8

Electron

Outermost electron shell (can hold 8 electrons)

First electron shell (can hold 2 electrons)

Empty spaces

IONIC BOND

ELECTRONS ARE

TRANSFERRED

POSITIVE charge

NEGATIVE charge

• When atoms gain or lose electrons, charged atoms called ________ are created– An electrical attraction between ions with opposite

charges results in an ___________ bond

Ionic bonds are attractions between ions of opposite charge

NaSodium atom

ClChlorine atom

Na+

Sodium ionCl–

Chloride ion

Sodium chloride (NaCl)

Na Cl Na Cl

+ –

Ionic Bonds• Form when 1 or 2 electrons are

transferred from one atom to another

• This creates an attraction between the two atoms – holds them together

• One becomes a __________ ion and the another _____________ ion

• ________ bond - Dissolves easily in water, usually

• Sodium and chloride ions bond to form sodium chloride, common table salt

Na+

Cl–

CHEMICAL BONDING II

Covalent bonds

are created when atoms ___________

electrons.

Electrons are shared!

How many more electrons can these atoms hold?

_______

• Some atoms SHARE outer shell electrons with other atoms, forming __________ bonds– Atoms joined together by covalent bonds

form molecules

– Very ________ bond

Covalent bonds, the sharing of electrons, join atoms into

molecules

• Molecules can be represented in many ways