PART II

LET’S FIRST REVIEW IONIC BONDING

In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS in ionic compounds. FK

FK + _ The compound potassium fluoride consists of potassium (K + ) ions and fluoride (F - ) ions

FK + _ The ionic bond is the attraction between the positive K + ion and the negative F - ion An ionic bond is a metal and nonmetal

So what are covalent bonds?

In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule).

In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair.

In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair. The shared electron pair is called a bonding pair

In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair. The shared electron pair is called a bonding pair A covalent bond is between a nonmetal and a nonmetal

Cl 2 Chlorine forms a covalent bond with itself

Cl How will two chlorine atoms react?

Cl Each chlorine atom wants to gain one electron to achieve an octet

Cl Neither atom will give up an electron – chlorine is highly electronegative. What’s the solution – what can they do to achieve an octet?

Cl The octet is achieved by each atom sharing the electron pair in the middle

Cl The octet is achieved by each atom sharing the electron pair in the middle

Cl This is the bonding pair

Cl It is a single bonding pair

Cl It is called a SINGLE BOND

Cl Single bonds are abbreviated with a dash

Cl This is the chlorine molecule, Cl 2

 These are atoms that are never, never, never found alone in nature.  H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

 There are 7 diatomic molecules

 Start with 7 on the periodic table  That would be Nitrogen (this is one of the diatomic molecules)

 Then make a number 7 on the periodic table

 Do not forget the 7 th diatomic molecule

Rules: 1. The formula is written with the more electropositive element (the one further to the left on the periodic table) placed first, then the more electronegative element (the one further to the right on the periodic table). Example : CO 2 [Important exception: when the compound contains oxygen and a halogen, the halogen is placed first. If both elements are in the same group, the one with the higher period number is named first.] Example: Cl 2 O.

2. The second element’s name ends in –ide 3. Never use the prefix mono with the 1 st word. 4. Do not put two O’s together

Naming covalent bonds Prefixes are used for the number of atoms 1 – mono 2 – di 3 – tri 4 – tetra 5 – penta 6 – hexa 7- hepta 8- octa 9- nona 10 - deca

Examples: CO 2 – CO – P 4 Cl 3 - Carbon Dioxide Carbon monoxide Tetraphosphorous trichloride

How will two oxygen atoms bond? OO

O2O2 Oxygen is one of the diatomic molecules

OO Each atom has two unpaired electrons

Oxygen atoms are highly electronegative. So both atoms want to gain two electrons. OO

Oxygen atoms are highly electronegative. So both atoms want to gain two electrons. OO

two bonding pairs, O O making a double bond

O O = For convenience, the double bond can be shown as two dashes. O O

Triple bonds are when three sets of electrons are shared.

Some covalent bonds can have more than one bond type.

OF COVALENT COMPOUNDS

Since electrons do not like each other, because of their negative charges, they orient themselves as far apart as possible, from each other. This leads to molecules having specific shapes.

Atoms bond to form an Octet (8 outer electrons/full outer energy level) Bonded electrons take up less space then un-bonded/unshared pairs of electrons.

Number of Bonds = 2 Number of Shared Pairs of Electrons = 2 Bond Angle = 180° EXAMPLE: BeF 2

Number of Bonds = 2 Number of Shared Pairs of Electrons = 2 Number of Unshared Pairs of Electrons = 2 Bond Angle = < 120° EXAMPLE: H 2 O

Number of Bonds = 3 Number of Shared Pairs of Electrons = 3 Number of Unshared Pairs of Electrons = 0 Bond Angle = 120° EXAMPLE: GaF 3

Number of Bonds = 3 Number of Shared Pairs of Electrons = 4 Number of Unshared Pairs of Electrons = 1 Bond Angle = <109.5° EXAMPLE: NH 3

Number of Bonds = 4 Number of Shared Pairs of Electrons = 4 Number of Unshared Pairs of Electrons = 0 Bond Angle = 109.5° EXAMPLE: CH 4

Number of Bonds = 5 Number of Shared Pairs of Electrons = 5 Number of Unshared Pairs of Electrons = 0 Bond Angle = <120° EXAMPLE: NbF 5

Number of Bonds = 6 Number of Shared Pairs of Electrons = 6 Number of Unshared Pairs of Electrons = 1 Bond Angle = 90° EXAMPLE: SF 6

Draw the following and state the shape 1.CCl 4 2.O 2 3.SBr 2 4.NI 3