Chapter 7

1

Chapter 7

Ionic and Metallic Bonding

2

Bonding--definition

Bonding

attractive forces binding ‘atoms’ or ‘ions’ together to form a cpd (ionic and covalent)

attractive forces holding ……

or

3

Compound

Compound atoms of different elements join together

chemicallytotally different in chem properties from the

elements …. Elements form cpds to increase in stabilityElectrically neutral A + B → A-----B Elements cpd

• e.g. Na + Cl2 → NaCl

bond

4

bonding

Form cpds

Ionic bond

Covalent bond

Pure metal

Metallic Bond

Intermolecular forces

H bond Van der waals Forces

Dipole-dipole

London dispersion

Ion-dipole

5

2 Types of Bonding—form cpds

1. Ionic bonding transfer e- → cations and anions Metal + nonmetal(s) Form ionic cpds (e.g. NaCl)

2. Covalent bonding share e- (no ions) Nonmetals only; (e.g. CO2, H2O) form covalent cpds (molecular cpds)

6

Compounds

Ionic cpdsCovalent cpds or molecular cpd

Ionic bondsCovalent bonds

Metal + nonmetal(s) nonmetals

e.g. MgO

formed by formed by

e.g. H2O

Transfer of e- Sharing e-

7

2 Types of Bonding— do not form cpds

*3. Metallic bonding in metallic elements does not form cpds.

*4. Hydrogen bonding between H and O, N, or F atoms (among

molecules) does not form cpds

8

Valence e-

Valence e- • e- in the highest EL of an atoms.

• # valence e- largely determines the chem properties of an element.

9

Valence e-

# of valence e- in an atom of (a representative element) = group # or the ones digit of the group #

10

7.1 Valence e-

11

The Octet Rule (1)

The Octet Rule

Atoms of what type of elements tend to lose e-?

Atoms of what type of elements tend to gain e- ?

Nonmetals: groups 5A, 6A, 7A

metals: groups 1A, 2A, 3A, B

12

The Octet Rule (2)In forming cpds, atoms tend to achieve the e- confign of a noble gas.

13

Ionic Bonding

Ionic bonding transfer e- Metal + nonmetal(s) Metals (1A, 2A, 3A, transition) lose e- to form

…→ cations Nonmetals (5A, 6A, 7A) gained e- to form … cations and anions attract each other →

Ionic cpd

14

Ionic Bonding

ionic cpds [metal + nonmetal(s)]

e.g. Na → Na+ + e- (loss) Cl + e- → Cl- (gain)

Na+ ~~ Cl-

Electrostatic attraction

Cation and anion attract each other by electrostatic force

15

Formation of Ionic Cpds

Formula Units (ionic cpds)

• the lowest whole-# ratio of ions in an ionic cpd.

•A chemical formula shows the kinds and #s of atoms in the smallest representative unit of a sub.

e.g. NaCl is a formula unit of sodium chloride—1 Na+ bonded to 1 Cl-

16

The Octet Rule (3)

Losing valence e- Atoms of metals tend to lose their valence e-

leaving a complete octet in the next-lower EL.

e .g. Na (1s22s22p63s1) loses 1 valence e ---- leave a Ne e-confign (1s22s22p6)→ Na+

Neon e- confign

17

The Octet Rule (4)

Gaining e- Atoms of some non-metals tend to gain e-

to achieve a complete octet.

e.g. Cl (1s22s22p6 3s23p5 ) achieve an e- confign of

Ar (Cl- 1s22s22p6 3s23p6 ) after gaining 1 e-Ar e- confign

18

Formation of Cations

An atom lost valence e- produces a cation (+ve).

e.g. Na → Na+ + e-Mg → Mg 2+ + 2 e-

e.g. Al →

cations

19


cations are produced by the loss of valence e- from metal atoms.

The e- loss (ionization) of the Na atom

Ne e- confign

20


The e- confign of the Na+ is the same as that of a Ne atom.

Na+

21

Na+ and NeDifferences

Similarity• same e- configuration • both octet

Na+ Ne

charge +ve charge none

# p+ 11 10

22


1 unit of +ve charge

1 unit of –ve charge

Na ion

23

Formation of Cations• A Mg atom attains the e- confign of Ne by

losing both valence e-. • The loss of valence e- produces a Mg cation

(Mg2+) with a charge of 2+.

(2 units of –ve charge)(2 units of

+ve charge)

24


• Cations of gp 1A 1+

• Cations of gp 2A

elements 2+

25

Formation of Anions

The gain of e- by a neutral atom → an anion.

• A particle derived from an atom (nonmetals) or a group of atoms

• Carries -ve charge(s) after gaining e-.

• many names of an anion ends in -ide.e.g. oxide, chloride, fluoride, sulfide, nitride, iodide,

26

Formation of Anions1A 5A 6A 7A anion

H H-

N N3-

P P3-

O O2-

S S2-

F F-

Cl Cl-

Br Br-

I I-

27

Formation of Anions

• A gain of 1 e- gives Cl an octet and converts a Cl atom into a chloride ion (Cl-).

• the same e- confign as the noble gas Ar.

28

Formation of AnionsBoth a Cl- and the Ar atom have an octet of e- in their

highest occupied ELs.

29

Formation of Anions

In this eqn, each dot in the e- dot structure represents an e- in the valence shell in the e- confign diagram.

7 valence e- Octet

30

Formation of Anions

halide ions ions produced when atoms of Cl and other

halogens gain e-.

• All halogen atoms need to gain only 1 e- to achieve the e- confign of a noble gas.

• Fluorides (F-), chlorides, bromides, iodide

31

Formation of Anions• O is in Gp 6A.

32

Ionic Charges of Some Ions1+ 2+ 3+ 3- 2- 1-

H+ H-

Li+ Be2+ N3- O2- F-

Na+ Mg2+ Al 3+ P 3- S2- Cl-

K+ Ca2+ Br-

Ag+ Ba2+ I-

Fe 2+ Fe 3+

Cu + Cu 2+

Zn 2+

Pb2+ Pb4+

33

Anions in Binary Cpds

1- 2- 3- F- fluoride O2- oxide N3- nitride

Cl- chloride S2- sulfide P3- phosphide

Br- bromide

I- iodide

34

Polyatomic Ions 1- 2- 3-

OH- hydroxide CO32- carbonate PO4

3- phosphate

NO3- nitrate SO4

2- sulfate

NO2- nitrite SO3

2- sulfite

HCO3- hydrogen

carbonate 1+ NH4

+ Ammonium

35

7.1 Formation of Anions

36

Metal Ions with more than 1 Ionic Charges Formula Stock Name

Cu+ Copper (I) ion

Cu 2+ Copper (II) ion

Fe 2+ Iron (II) ion

Fe 3+ Iron (III) ion

Pb 2+ Lead (II) ion

Pb 4+ Lead (IV) ion

Cr 2+ Chromium (II) ion

Cr 3+ Chromium (III) ion

Mn 2+ Manganese (II) ion

Mn 4+ Manganese (IV) ion

37

Highly Unequal Sharing

Ionic Bond e- transfer results in the formation of 1 +ve

ion and 1 -ve ion.Metal ~ nonmetal

The bond formed by the 2 oppositely charged ions.

Cation ~~anion

Electrostatic attraction

38

A Model of Bonding

• By forming bonds, atoms acquire an octet of e- and the stable e- confign of a noble gas.

• Atoms are often more stable when they’re bonded in cpds than when they’re free atoms.

39

Formation of Ionic CpdsIonic Bonds The electrostatic forces that hold ions together

in ionic cpds are called ionic bonds.

40

Physical Properties of Properties Ionic cpd Covalent cpd

Example NaCl CO 2

State at room temperature

Crystalline solid Solid, liquid or gas

Melting point High Low

Conduct electricity in liquid state

Yes No

Water solubility Usually High Low

Conduct electricity in aq soln

Yes No

41

Atomic View of Metallic Bonding

• Each atom in this model of a Gp 2 metal releases its 2 valence e- into a sea of e- to be shared by all of the metal atoms.

• Delocalized e-

42

Sea of Valence e-

• The valence e- of metal atoms are loosely held by the +vely charged nucleus.

• In metallic bonding, metal atoms don't lose valence e-.

• Not forming cpds

43

Sea of Valence e-

metallic bond• Metal atoms release valence e- into a sea of

e- shared by all of the metal atoms.

• Attraction between e- sea and the metal atoms (cations)

44

Atomic View of Metallic Bonding

• Bonding in metals is not rigid.

• The same ability to reorganize explains why metals …

As a metal is struck by a hammer, the atoms slide thru the e- sea to new positions while continuing to maintain their connections (bond) to each other.

45

Properties That Reflect Metallic Bonding

Conductors of electricity the valence e- are freely moving and is

charged.Electric current is a flow of e-

46

Properties That Reflect Metallic Bonding

Metals and alloys are malleable made into thin sheets

47

Properties That Reflect Metallic BondingMetals are Ductile can be drawn into wires.

48

CST problem 1When cations and anions join, they form what

kind of chemical bond?A ionicB hydrogenC metallicD covalent

49

CST problem 2The reason salt crystals, such as KCl, hold

together so well is because the cations are strongly attracted toA neighboring cationsB the protons in the neighboring nucleusC free electrons in the crystalsD neighboring anions.

50

The End

51

Properties of Ionic Cpds

The coordination # of an ion the # of ions of opposite charge that surround the

ion in a crystal.

In NaCl, each ion has a coordination # of 6.

52

Properties of Ionic Cpds• In CsCl, each ion has a coordination # of 8. • In TiO2, each Ti4+ ion has a coordination # of 6, while

each O2- ion has a coordination # of 3.

53

Formation of Ionic Cpds

NaCl is the chem formula for sodium chloride.

54

Properties of Ionic Cpds

Ionic cpds can conduct an electric current when melted or dissolved in water.

Chapter 7

Documents

Transcript of Chapter 7