5. giant covalent and metallic

Question 1

what factor impacts

METALLIC BOND STRENGTH?

Answer 1

Depends on the number of outer electrons donated to the cloud and the size of the metal atom/ion.

MELTING POINT INCREASES ACROSS THE PERIOD

THE ELECTRON CLOUD DENSITY INCREASES DUE TO THE
GREATER NUMBER OF ELECTRONS DONATED PER ATOM. AS A
RESULT THE IONS ARE HELD MORE STRONGLY.

eg. The strength of the metallic
bonding in sodium is
relatively weak because each
atom donates one electron to
the cloud.

The metallic bonding in
magnesium is stronger than
in sodium because each atom
has donated two electrons to
the cloud. The greater the
electron density holds the
ions together more strongly.

Question 2

properties of

Covalent molecular structures

Answer 2

Small discrete molecules

Strong covalent bonds within molecules

Weak intermolecular forces between
molecules

Many of these structures dissolve in organic
solvents; some dissolve in water

Typical examples – CO2 , H2O, Br2, S8

Question 3

properties of

giant covalent structures

Answer 3

• Giant repeating lattices of
  very many covalently
  bonded atoms
• Insoluble solids with high
  melting and boiling points
• Typical example is SiO2

Question 4

define

Allotropes

Answer 4

Different structures of the same element are
called allotropes

Question 5

what are the 4

allotropes of carbon

Answer 5

1. graphite (makes 3 bonds)
2. graphene
3. buckminsterfullerene C60
4. diamond (4 bonds)