Chemical Bonding

How does bonding occur?

• Chemical bonding – the combining of atoms of elements to form new substances.

• The rules of chemical bonding are determined by the structure of the atom. The valence electrons determines if it will bond or not.

Bonding

• If an atom has 8 valence electrons it is stable and will not bond

• An atom with less than 8 valence electrons is unstable and will bond readily (easily)

• The ability to bond determines its ability to undergo chemical reactions

BondingNumber of valence: What happens:1, 2, 3 lose electrons5,6,7 gain electrons4 gain or lose8 unresponsive.. Nada.. nothing

1. Ionic bonding – involves a transfer of electrons. One atom gains and the other one loses (metal and non-metal)

Forms Ions – a charged atom (positive or negative).

2. Covalent bonding –They share electrons, rather than transfer. (Non-metal and non-metal), form molecules

3. Metallic bonding: metal and metal, electrons are able to fly off the energy levels

WHICH TYPE OF BOND IS THIS?

1. H + Cl =2. Sc + Hf =3. O + P =

Ionic Bonding • Ionic bonding – involves a transfer of electrons. One

atom gains and the other one loses.

• Ion – a charged atom (positive or negative).

• Example: Fluorine (F) has 7 valence electrons and to become stable, it gains 1 electron to fill its outermost level and becomes a negative ion.

Remember all atoms want 8 valence electronsMETALS AND NON METALS BOND

Ionic Bonding

Electron transfers to other atom

Covalent bonding• Covalent bonding – occurs between atoms that

have high ionization energy (a lot of valence electrons) and high electron affinity (attracts electrons)

• They share electrons, rather than transfer. “Co” means to share.

• Simplest example: Hydrogen H : H

COVALENT BONDING

Electrons are shared by both atoms

More about covalent bonds…

• Covalent bonds form molecules. • A molecule is the smallest particle of a

covalently bonded substance that shares all the properties of that substance.

NONMETAL AND NONMETAL

Bonds

Metallic Bonding • Metallic bonding – bond when the positive nuclei

are surrounded by mobile electrons. (all attracted at the same time). This allows the metals to be heat conductors.

• Referred to as the “sea of electrons”

• This is when the electrons are able to come off of their electron orbits and move freely.

METALS AND METALS

Electrons flying off energy levels

Vocabulary1. Chemical bonding – the combining of atoms of elements to form

new substances2. Ion – a charged atom (positive or negative).3. Ionization – the process of removing electrons to form ions. 4. The energy needed to remove the electrons is called ionization

energy.5. Electron affinity – the tendency of an atom to attract electrons.6. Polyatomic ion – when two elements bond first covalently then

through ionic bonding7. Oxidation number – the number of electrons an atom gains or

loses, or shares in a chemical bond.8. Diatomic elements – form bonds with atoms of the same

element.