ORGANIC CHEMISTRY

Unit 1 – Atomic and Molecular Structures (Bonding Review)

The Atom

• 2 Parts = Nucleus and electron (e-)cloud • Nucleus – small, dense positively charged region in the center of the atom (almost all of its mass and none of its volume) • e- Cloud – area surrounding the nucleus where the e-s may be found

The Electron Cloud

• e- = negatively charged subatomic particle found outside the nucleus • e-’s are found in energy levels (shells ) from 1  ?

• shells are divided into sublevels (subshells) • shells contain orbitals (3-d region around the nucleus where an e- may be found)

Electron Shells

Orbital Review

• SPDF – 2 e-s per orbital – with opposite spins!

• s = 1, p = 3, d = 5, f = 7) • Quantum Numbers (QN) • Principal QN – n = E level • Angular Momentum QN – l = shape • Magnetic QN – m = orientation • Spin QN – direction

Electron Configurations

• 1. Pauli Exclusion Principle – no 2 e-‘s in the same atom can have the same set of 4 quantum numbers • The two e-‘s in an orbital have to have opposite spins ( ) • 2. Aufbau Principle – an e- will occupy the lowest E orbital that can accept it • 3. Hund’s Rule – orbitals of equal E must each have 1 e- before any can get 2

Electron Configurations

• Writing e- configurations : we use orbital notation & e- config. Notation • Principal QN = n 2n 2 = # e-‘s in an e- shell • Try the configurations for Na, O, Fe, and Xe • Try the orbital notation (orbital diagrams) for the same elements listed above.

• Some exceptions in Transition, 4f, and 5f

Stability

• Atoms try to become stable by filling their outer e- shell (8e-‘s) • Octet = full shell of 8 e-‘s in the outer shell (s & p orbitals) • Full octet = Noble Gas Configuration • Elements form compounds to gain octet configurations • Either transfer outer shell e-‘s to form ionic bonds, or by sharing e-‘s to form covalent bonds

Noble Gas Notation

• Used for elements beyond K • Practice the NGN for Ni, Sn, and Ba

Electron Dot Symbols (Lewis Structures)

• Show outer e-’s (s and p orbitals) • Used to show chemical bonds • Draw the next chart in your notebook and fill in the blanks with the correct information 

Lewis Structures

Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Li•

•Be• • • B • • • C • • • • N : • • : O : • • • : F : • • • : Ne : • •

Lose 1 e-

Lose _ e Lose _ e Shares e- Gains _ e- Gains _ e- Gains _e- Does not bond

+ 1 ion

__ ion __ ion __ ion __ ion __ ion (Already Stable)

Lewis Structures

Group 1 Li• Group 2

•Be•

Group 3

• • B •

Group 4

• • C • •

Group 5

• • N : •

Group 6

• : O : •

Group 7

• • : F : •

Group 8

• • : Ne : • •

Lose 1 e-

Lose 2 e Lose 3 e Shares e- Gains 3 e- Gains 2 e- Gains 1 e- Does not bond

+ 1 ion

+ 2 ion + 3 ion - 1 ion - 2 ion - 3 ion (Already Stable)

LS for Molecules

• Ionic Bonds are formed by metals from Groups I, II, or III giving e-’s for • nonmetals from Groups VI, VII, or VII Try the LS and Orbital Diagrams for K 2 S, Na 3 N, and CaF 2

Bonding

• Gr I = bonds ns 1 • Gr II = bonds *ns 1 np 1 • Gr III = bonds * ns 1 np 2 • Gr IV = bonds * ns 1 np 3 • Group V = bonds ns 2 np 3 • Group VI = bonds ns 2 np 4 • Group VII = bonds ns 2 np 5 * = excited State n = E Level (Outer Shell)

Why promote an s e-?

Bonding Examples

• Try AlI 3 , Ca 3 N 2 , SrS

Covalent Bonding

• Covalent bonds are formed when Groups IV – VII (and H) share outer shell e-s so each atoms gets 8 e-s (except H can only get 2 e-s) • There are 4 kinds of covalent bonds (right now = look at 3 of them) • Remember diatomic elements  NOAH

Covalent Bonding

• Single Covalent Bond – one pair of e-s shared between 2 atoms • F 2 • Lewis Structure = • Orbital Diag. =

Covalent Bonding

• Double Covalent Bond – two pairs of e-s shared between 2 atoms • O 2 • Lewis Structure = • Orbital Diag. =

Covalent Bonding

• Triple Covalent Bond – three e- pairs shared between 2 atoms • N 2 • Lewis Structure = • Orbital Diag. =

Covalent Bonding

• When Drawing Lewis Structures for covalent structures, start with only 2 atoms and add alternatively as you need them • NCl 3

Homework!

• Complete the following Lewis Structures for Covalent Compounds for homework: • H 2 O/ SBr 2 / CBr 4 / NP/ CO 2 / N 2 O 3 / Na 2 Te/ BaSe

Polyatomic Ions

• We can also take the same approach with polyatomic ions • Polyatomic Ion – covalently bonded group of atoms that carries a net charge • Negative polyatomic ions are formed by H + ions leaving an oxyacid • Oxyacid – an acidic substance that contains oxygen • Positive polyatomic ions are formed by H + ions bonding coordinately to a neutral molecule

In Class Assignment

• Do the Lewis Structures for the following… • [HSO 4 / SO 4 2 / H 2 PO 4 / HPO 4 -2 / PO 4 -3 / HCO 3 / NO 3 / IO 3 / CO 3 -2 / NH 4 + / PH 4 + / H 3 S + / H 2 Cl + / H 4 I 3+ ]

Last Covalent Bonding Type

• Coordinate Covalent Bond – a bond where both shared e-s are from the same • species (bond between a Lewis acid and a Lewis Base)