Chemical Bonding

Monday November 3rd, 2008

What is a chemical bond?What is a chemical bond?

• A bond is a force that holds two or more atoms together and makes them function as a unit or a group.

• A bond is a force that holds two or more atoms together and makes them function as a unit or a group.

Why are bonds important in chemistry?

Why are bonds important in chemistry?

• Atoms that are bonded together function as one particle in nature/mixtures

• It is the bonds that are broken and reformed in a chemical reaction

• Not all bonds in a molecule are broken in a chemical reaction.

• Atoms that are bonded together function as one particle in nature/mixtures

• It is the bonds that are broken and reformed in a chemical reaction

• Not all bonds in a molecule are broken in a chemical reaction.

How do bonds form?How do bonds form?

• Atoms must be close enough to each other for their electrons to interact

• Atoms that are close enough together must WANT to form bonds• Atoms form bonds to achieve stable

electron configuration in their valence shells

• Remember “Eight is Great”

• Atoms must be close enough to each other for their electrons to interact

• Atoms that are close enough together must WANT to form bonds• Atoms form bonds to achieve stable

electron configuration in their valence shells

• Remember “Eight is Great”

Types of BondsTypes of Bonds

• Three types of bonding• The names describe the

relationship of the electrons in the atoms to each other, and between the two nuclei• Ionic bonds• Polar Covalent bonds• Covalent Bonds

• Three types of bonding• The names describe the

relationship of the electrons in the atoms to each other, and between the two nuclei• Ionic bonds• Polar Covalent bonds• Covalent Bonds

Covalent Bonds(Two nonmetals)Covalent Bonds

(Two nonmetals)• Electrons are equally shared

between the two atoms (nonmetals)

• The shared electrons are found between the nuclei of the two atoms

• Electrons are equally shared between the two atoms (nonmetals)

• The shared electrons are found between the nuclei of the two atoms

Polar Covalent Bond(Two nonmetals)

Polar Covalent Bond(Two nonmetals)

• Electrons are shared UNEQUALLY between atoms (nonmetals)

• The shared electrons are found between the nuclei, but they are attracted to one nucleus (atom) more than the other nucleus (atom)

• Electrons are shared UNEQUALLY between atoms (nonmetals)

• The shared electrons are found between the nuclei, but they are attracted to one nucleus (atom) more than the other nucleus (atom)

Ionic Bonds(metal and nonmetal)

Ionic Bonds(metal and nonmetal)

• The electrons are completely transferred from one atom to another

• The atoms in the bonds become IONS• One atom becomes a positive ion, while

the other atom becomes a negative ion• In ionic bonds, all atoms will lose or gain

electrons to complete their valence shells

• 8 is great!

• The electrons are completely transferred from one atom to another

• The atoms in the bonds become IONS• One atom becomes a positive ion, while

the other atom becomes a negative ion• In ionic bonds, all atoms will lose or gain

electrons to complete their valence shells

• 8 is great!

Binary Ionic CompoundsBinary Ionic Compounds

• Binary = two• Binary compounds have two

elements in them• Binary Ionic Compounds have two

elements that are bonded by an ionic bond

• One element MUST be a metal, and the other MUST be a non-metal

• Binary = two• Binary compounds have two

elements in them• Binary Ionic Compounds have two

elements that are bonded by an ionic bond

• One element MUST be a metal, and the other MUST be a non-metal

MetalsMetals

• Lose their valence electrons to form ions

• Form positive ions• Attain “Noble Gas” configuration of

the Noble Gas in the preceding row (row above the element)

• The name of the ion is the same as the element

• Lose their valence electrons to form ions

• Form positive ions• Attain “Noble Gas” configuration of

the Noble Gas in the preceding row (row above the element)

• The name of the ion is the same as the element

Non-MetalsNon-Metals

• Gain electrons to form ions• Form negative ions• Attain Noble Gas configuration

(stable) of the Noble Gas following (the same period)

• The ion is named by dropping the ending and adding the suffix -ide• i.e chlorine becomes chloride

• Gain electrons to form ions• Form negative ions• Attain Noble Gas configuration

(stable) of the Noble Gas following (the same period)

• The ion is named by dropping the ending and adding the suffix -ide• i.e chlorine becomes chloride

Ionic CompoundsIonic Compounds

• All compounds are NEUTRAL• The sum of the charges of all of the

ions in an ionic compound must be electrically neutral (no charge)

• Therefore, the sum of the positive and negative charges must be equal

• The numbers of atoms might not be equal

• All compounds are NEUTRAL• The sum of the charges of all of the

ions in an ionic compound must be electrically neutral (no charge)

• Therefore, the sum of the positive and negative charges must be equal

• The numbers of atoms might not be equal

Binary Ionic Compound Examples

Binary Ionic Compound Examples

NaClNa+ + Cl-

CaCl2Ca+2 + 2Cl-

NaClNa+ + Cl-

CaCl2Ca+2 + 2Cl-

What do the numbers mean?

What do the numbers mean?

CaCl2The 2 represents that there are 2

chloride atoms (ions) for every Calcium ion in the compound

Ca+2 + 2Cl-

CaCl2The 2 represents that there are 2

chloride atoms (ions) for every Calcium ion in the compound

Ca+2 + 2Cl-

Why is that?Why is that?

Ca+2 + 2Cl- _____________________

Total Charge: +2 -2

The charge on the compound must equal zero

Ca+2 + 2Cl- _____________________

Total Charge: +2 -2

The charge on the compound must equal zero