unit 1 – atomic and molecular structures (bonding review) organic chemistry

Unit 1 – Atomic and Molecular Structures(Bonding Review)

ORGANIC CHEMISTRY

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 2n2 = # 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 StructuresGroup 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 StructuresGroup 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 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 K2S, Na3N, and CaF2

Bonding•Gr I = bonds ns1

•Gr II = bonds *ns1np1

•Gr III = bonds * ns1np2 * = •Gr IV = bonds * ns1np3 excited State•Group V = bonds ns2np3

•Group VI = bonds ns2np4 n = E Level•Group VII = bonds ns2np5 (Outer Shell)Why promote an s e-?

Bonding Examples•Try AlI3, Ca3N2, 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•F2

•Lewis Structure =

•Orbital Diag. =

Covalent Bonding•Double Covalent Bond – two pairs of e-s shared between 2 atoms•O2

•Lewis Structure =

•Orbital Diag. =

Covalent Bonding•Triple Covalent Bond – three e- pairs shared between 2 atoms•N2

•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•NCl3

Homework!•Complete the following Lewis Structures for Covalent Compounds for homework:•H2O/ SBr2/ CBr4/ NP/ CO2/ N2O3/ Na2Te/ 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…•[HSO4

-/ SO4-2/ H2PO4

-/ HPO4-2/

PO4-3/ HCO3

-/ NO3-/ IO3

-/ CO3-2/

NH4+/ PH4

+/ H3S+/ H2Cl+/ H4I3+]

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)