Understanding the Properties of Ionic, Metallic, and Covalent Solids, Lecture notes of Chemistry

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Structure

and^

Properties

of^ Solids

Ionic

Metallic

Covalent

Network

Structure

and^

Properties

of^ Solids

We^ need

to^ use:

-^ ionic,^

covalent

and^ metallic

bonding

and •^ molecular,

ionic,^ metallic

and^ covalent

network

structure

To^ explain

properties

of^ substances:

-^ melting

and^ boiling

points,^ solubility,

electrical

conductivity,

malleability,

ductility,

and^ hardness.

Ionic

Compounds

Bonding Ionic^ compounds

consist^ of

ions^ held

together

by

ionic^ bonds.

Ionic^ bonds

are^ strong

bonds.

Structure These^ bonds

hold^ ionic

compounds

together

in^ a

regular^3

‐dimensional

lattice.^ Each

ion^ is

surrounded

by^ ions^ of

the^ opposite

charge.

Structure

and^ bonding

in^ ionic

compounds

ionic^

ions^

ionic^ bonds

Properties

of^ ionic

compounds

Brittleness…Ionic^ compounds

are^ brittle

because

of^ their^

3 ‐dimensional

lattice^ structure.

If^ they^ are

knocked

out^ of^ line

the^ anions

repel

the^ anions

and^ the^

cations repel

the^ cations and

the^ compound

breaks^ apart.

+^ ‐+‐‐ +++‐^ ‐ +^ +‐‐‐ +++ ‐^ ‐

+^ ‐+‐‐ +++ ‐^ ‐ + +‐‐‐ +++ ‐ ‐

Malleability

and^ ductility… Ionic^ compounds

are^ not^ malleable

or^ ductile

as^ the^ ionic

bonds^ are

directional

Do^ now:

Why^ are some^ ionic

compounds

soluble^ in^ water?

Why^ do^ ionic

compounds

have^ high

melting^

points?

Why^ can

ionic^ compounds

not^ conduct

electricity

when^ they

are^ solid?

Bonding Metallic^

compounds

consist^ of

positive

nuclei

surrounded

by^ electrons.

The^ nuclei

and^ electrons

are^ held

together

by^ metallic

bonds.^ Metallic

bonds^ are

strong^ bonds.

Structure

and^ bonding

in^ metallic

compounds

In^ the^ exam

you^ will be^ asked

to^ fill^ in^

a^ table^ like

this:

metallic^

atoms^

metallic^

bonds

Structure Metallic^

bonds^ are

non‐directional,

and^ the^

sea^ of^ electrons

surround

the^ positive

nuclei.

Sea^ of^

electrons

Metallic^

bonds^ are

strong but^ non‐

directional

(the nuclei^ can

move^ around). The^ electrons

are^ the valence^ electrons

of^ the metal^ (the

electrons

from the^ outer

shell^ of^ the atom).

Properties

of^ metallic

compounds

Melting^ point…Metallic^

compounds

have^ high

melting^

points^ because

a^ lot^ of

energy^ is

required

to^ break

the^ electrostatic

attractions

between

the^ cations and

electrons. Conductivity…Metallic^

compounds

can^ conduct

electricity

as^ there

are^ electrons

free^ to^ move. Solubility…Metallic^

compounds

are^ not^ soluble^ in

water,^ as

the^ water

can^ not

pull^ the^ cations away

from^ the

electrons.

Properties

of^ metallic

compounds

Malleability

and^ ductility… Metallic^

compounds

are^ ductile

(stretchy)

and^ malleable

(bendy)

because^

the^ metallic

bonds^ are

non‐directional

(sea^ of^ electrons

allow^ the

nuclei^ to

move). Brittleness…Metallic^

compounds

are^ not^ brittle^ because

the^ metallic

bonds^ are

non‐directional

(sea^ of^ electrons

allow^ the

nuclei^ to

move).

Do^ now:

In^ your^ own

words^ explain

the^ similarities

and^ differences

between

metallic

and^ ionic

structure.

METALLICeg^ copper

IONICeg sodium chloride^ (salt)

GIANT MOLECULAReg diamond, graphite

SIMPLE^ MOLECULAReg carbon Types^ of COVALENT^ dioxide,^ water

bonds

Bonding The^ atoms

in^ covalent

network

compounds

are^ held

together

by^ covalent

bonds.^ Covalent

bonds^ are

strong.

Structure Diamond

and^ silica

• atoms

are^ covalently

bonded in^ regular

dimensional

networks,

each^ atom

is^ bonded

to^4 other

atoms.

Graphite

• atoms

are^ covalently

bonded^

in^2 ‐dimensional

sheets^ with

free^ electrons

between

the^ sheets,

each^ atom

is

bonded^ to

3 other^ atoms.

Structure

and^ bonding

in^ covalent

network

compounds

covalent network

atoms^

covalent bonds

Do^

now:

What^ type

of^ substance

am^ I? (a) I^ have

a^ melting

point^ of

>3500^ °C

and^ can not^ conduct

electricity.

I^ am^ an^

colourless

crystal.^ Am

I^ an^ ionic

compound

or^ metallic

compound

or^ covalent

network

compound?

(b) I^ have

a^ melting

point^ of

801 °C^ and

I^ shatter

easily.^ I^ don’t

conduct^

charge^ when

I^ am^ a^ solid

but^ I^ can

when^ I^ am

molten.

Am^ I^ an^ ionic

compound

or^ metallic

compound

or^ covalent

network compound? What^ aspects

of^ structure

and^ bonding

give^ these

substances

their

properties?