Covalent BondingSharing on an atomic level

Why do Atoms bond? Gain Stability

Ionic bonds gain stability by gaining or losing electrons.

What happens if the pull isn’t strong enough to take or give up an electron?

Covalent bonding Results from

sharing valence electrons.

The pull isn’t enough to take the electron away.

Forms a Molecule Two or more

elements bonded together.

How many bonds

Group 17 Single bond To another non-

metallic element Group 16

2 single bonds

Group 15 3 single bonds

Group 14 4 single bonds

A single bond is formed when one pair of electrons is shared betweenTwo elements.

The sigma bond Single bonds are

called sigma bonds

σ bonds can be the overlap between two s orbitals or two p orbitals or and s and p.

Homework• For Friday please practice

drawing covalent bonds for the following

• On page 244 1-5• PH3

• H2S• HCl• CCl4• SiH4

Multiple bonds The double bond Have you ever thought about the

difference between the oxygen we breath and ozone?

They both are made of only oxygen atoms, but they are different.

It has to do with how they bond.

The difference is the double bond

O2 O3

Why? How does it happen? Take the next minute and a half and talk

to your table partner about it. Ideas?

A second option In ionic bonds it was about equalizing

charges. In covalent bonds it is about making paired

electrons If an atom is able to make a single bond

and they both still have an unpaired electron. Which makes more sense to have both of them try to find another atom or for them to pair again with each other?

Triple bonds A bond that is formed by sharing three

pairs of electrons. This can only happen if all three pairs

are on the atom. N and C families

Pi bond A σ bond was for a single bond A π bond is formed for any double or

triple bond. They look different because they cannot

occupy the same space.

Shapes What is happening in the process of

bonding? Electrons are coming together. They are

all – charged and so they repel each other.

So they are going to get as far away from each other as possible and still stay connected to the atoms.

So lets visualize Ionic bonds- Girls are Cations and Boys

are Anions. Every one has a 1 charge. Covalent bonds Girls are carbons and

Boys are hydrogens. Pair up

Molecular structure and naming

Moving from Lewis dot to Structural formula You have been using Lewis dot

structures and molecular formulas Now we simplify it with structural

formulas Structural formulas use symbols and

bonds to show relative position of atoms.

Figuring out number of bonds Atoms that make the most connections

go in the center Determine the number of electrons

available for bonding Divide that number in half to find the

number of bonding pairs Use as many of your bonding pairs for

single bonds Remaining bonding pairs will make

double or triple bonds

PracticeMolecular Formula Lewis Structure Structural Formula

PH3

CH4

CCL4

O2

PracticeMolecular Formula Lewis Structure Structural Formula

Resonance Structures Resonance is when more than one

structure can be written for a molecule or ion.

Exceptions to the Octet rule Odd numbers of valence electrons

N+O2= how many total electrons? 5+ 6+6= 17 They cannot be paired up.

Suboctets A lone pair of electrons can be shared by

a group that doesn’t have a spot BH3 + NH3

Expanded Octets When the atom forms more bonds and

shares more than eight electrons. PCl5 SF6

Naming Covalent bonds Naming Gases Very few things stay gas at room temperature. But for those that do we name them by ending

their name with gas It is important for knowing how many elements

you are talking about. Oxygen gas means you have 2 atoms of

oxygen. Chlorine gas? Helium gas?

Naming Molecules Binary compounds1. The first element in the formula is always

named first, using the whole element name.2. The second element in the formula is

named using the root and changing the end to ide.

3. Prefixes are used to indicate the number of atoms of each element that are present. Ex. Monoxide, dioxide, tetrafloride.

Number of Atoms Prefix1 Mono- (Used only for oxygen)2 Di-3 Tri-4 Tetra-5 Penta-6 Hexa-7 Hepta-8 Octa-

Naming Acids binary The first word has the hydro to name

the hydrogen part of the compound The rest of the first word consists of a

form of the root of the second element plus the suffix –ic.

The second word is acid. Hydrochloric acid HCl

Naming Acids oxyacids First identify the oxyanion present. The

first word of an oxyacid’s name consists of the root of the oxyanion and the prefix(if it exists) and the suffix. Suffix ate is released with ic ite is replaced with ous

The second word is always acid Sulfuric acid H2SO4