Bonding Part II Unit 5 – Bonding Mrs. Callender

Lesson Essential Questions: What are the characteristics of covalent bonds? How are covalent bonds formed?

Bonding Forces that hold groups of atoms together and make them function as a unit.

BONDING COVALENT Bonds Sharing of Electrons. Covalent compounds tend to form so that each atom, by sharing electrons, has an octet of electrons in its highest occupied level. These compounds involve nonmetals only. The term molecule is used exclusively for covalent bonding.

The OCTET Rule: The Diatomic Fluorine Molecule Diatomic – Elements that only exist in pairs. H 2, O 2, F 2, Br 2, I 2, N 2, Cl 2. Remember HOFBrINCl F 1s2s2p F 1s2s2p Each has seven valence electrons. F Two electrons between elements make one bond. It is represented with a line.

The OCTET Rule: The Diatomic Oxygen Molecule Diatomic – Elements that only exist in pairs. H 2, O 2, F 2, Br 2, I 2, N 2, Cl 2. Remember HOFBrINCl O 1s2s2p O 1s2s2p Each has six valence electrons. O Two pairs of electrons between elements makes a double bond.

The OCTET Rule: The Diatomic Nitrogen Molecule Diatomic – Elements that only exist in pairs. H 2, O 2, F 2, Br 2, I 2, N 2, Cl 2. Remember HOFBrINCl N 1s2s2p N 1s2s2p Each has five valence electrons. N Three pairs of electrons between elements indicates a triple bond.

The HONC Rule Hydrogens and Halogens form one covalent bond. Oxygen and Sulfur form two covalent bonds. One double bond or two single bonds. Nitrogen and phosphorus form three covalent bonds. One triple bond, one double and one single bond, or three single bonds. Carbon and Silicon form four covalent bonds. One triple bond and a single bond, two double bonds, four single bonds, or a double bond with two single bonds.

Completing a Lewis Dot Structure – CH 3 Cl 1.Evaluate the compound by looking at each elements valence electron amounts. C 1s 2 2s 2 2p 2 4 valence electrons. H 1s 1 1 valence electron x 3 for H 3 Cl 1s 2 2s 2 2p 6 3s 2 3p 5 7 valence electrons. 2. According to HONC – Carbon can bond to four other elements but hydrogen and chlorine will only bond once therefore Carbon will be the center of the molecule.

We know we have 14 total electrons to work with. 4 e- from C + 3(1) e- from H + 7 e- from Cl = 14 e- Carbon will be centrally located in the molecule with the other elements surrounding it. CH Cl H H Each element to element needs a pair electrons for a bond. Complete octets on elements except for hydrogen with remaining electrons. 14 – 8 = 6 electrons. For each shared pair of electrons draw a line. Leave the unshared pair of electrons as dots.

Bond Length and Energy BONDLength (pm)Energy (KJ/mole) C-C C=C C=CC=C C-N C=N C=NC=N C-O C=O C=OC=O N-N N=N N=NN=N110942

RESONANCE Occurs when more than one valid Lewis Dot Structure can be written for a particular molecule. This is a resonance structure for ozone, O 3. The actual structure is an average of both.

Draw the following compound: PBr 3 5 e- from P + 3(7) e- from Br = 26 e- Phosphorus will be centrally located in the molecule with the other elements surrounding it. PBr Each element to element needs a pair electrons for a bond. Complete octets on elements with remaining electrons. 26 – 6 = 20 electrons. For each shared pair of electrons draw a line. Leave the unshared pair of electrons as dots.

Draw the following compound: NH e- from N + 4(1) e- from H = 9 e- but since it is positive you must subtract another e- so the total is 8 e-. Nitrogen will be centrally located in the molecule with the other elements surrounding it. N HH H Each element to element needs a pair electrons for a bond. +1 Since this is an ion it needs placed in brackets with the charge in the upper right hand corner. H