bonding in solids in molecular solids, the particles are held to each other by imfs. -- mol. solids...

Bonding in Solids

In molecular solids, the particlesare held to each other by IMFs.

-- mol. solids are soft, w/low MPs

805

111–95*

18243

benzene

CH3 OH

toluene phenol

BP (oC)MP (oC)

Why?nonpolar;

weak LDFs

*stronger LDFs than C6H6, but doesn’t pack as closely in

solid form

H-bonding (strongest IMF)

In covalent-network solids, particlesare held together in large networksby covalent bonds.

-- harder – and have higherMPs – than molecular solids model of covalent-

network solid

-- e.g., diamond, graphite

model of molecular solid

In a molecularsolid, the particles

are held to eachother by IMFs. IMFs

good conductoralong its layers.

NOTE: Graphite has layers of covalently-bonded C atoms w/delocalized, p e–s (similar to benzene). Therefore, graphite is a...

The layers are held to each other by… weak LDFs.

e–e–

e–e–e–

e–

e–e–e–

e–

e– e–

e–e– e– e–

e–

e–e–

e–e–

+

–

Ionic solids consist of ions heldtogether by ionic bonds.

-- MPs depend largely on magnitude of charges.

-- e.g., MP of KCl = ______; MP of CaO = ______

776oC2572oC

Ionic size is a lesser factor.

potassium chloride (KCl) calcium oxide (CaO)

Metallic solids consist entirely of metal atoms.

-- these have HCP, CCP/FCC, or BCC structures, w/each atom touching 8 or 12 others

-- bonding is due to delocalized valence e– that are free to move throughout solid

** responsible for metallic properties(good heat and elec. conductors,

ductile/malleable, etc.)

-- metallic bond strength increases w/# of v.e–

e.g. MP of Li = ______; MP of Fe = ______ 181oC 1538oC

C-only or Si-anything: covalent-network

nonmetals only (including C-anything): molecular

metals only: metallic

metal-nonmetal: ionic

Metallic Properties

-- heat and elec. conductivity…

v.e– are free to move throughout material.

-- Via the v.e–, atoms w/high thermal energy can pass it on to others w/less.

-- Since the v.e– are charged (i.e., negatively), a DV causes them to migrate as a group.

e– e– e– e–

e– e– e– e– e– e– e– e– e– e– e– e–

e– e– e– e– e– e– e– e–

A spool of copper wire. Cu is anexcellent conductor, second only

to Ag (and followed by Au and then Al).

Metallic Properties, cont.

-- ductility/malleability…

e– e– e– e–

e– e– e– e– e– e– e– e– e– e– e– e–

e– e– e– e– e– e– e– e–

e– e– e– e–

e– e– e– e– e– e– e–

e–

e–

e–e–

e–

e– e– e– e–

e–

e–

e–e–

e–e–

e–

e–

e–

e–

(Some are pushed closer together,some are stretched farther apart).

The mobile v.e– move to counteractthose stresses.

Because v.e– in ionic and covalentsolids aren’t mobile, thesesubstances are insulators andare generally brittle.

When a metal is bent, the nucleiand core e– are forced into anonuniform arrangement.