C3(3.1-3.12) Structure and Bonding Flashcards
How are covalent bonds formed?
-By atoms sharing electrons
Which type of atoms form covalent bonds between
them?
-Non-metals
Describe the structure and bonding of a giant
covalent substance.
-Billions of atoms bonded together by strong covalent
bonds
Describe the structure and bonding of small
molecules.
-Small numbers of atoms group together into molecules
with strong covalent bonds between the atoms and
weak intermolecular forces between the molecules
Describe the structure and bonding of polymers
Many identical molecules joined together by
strong covalent bonds in a long chain, with weak
intermolecular forces between the chains
Why do giant covalent substances have high
melting points?
-It takes a lot of energy to break the strong covalent
bonds between the atoms
Why do small molecules have low melting points?
-Only a small amount of energy is needed to break the
weak intermolecular forces
Why do large molecules have higher melting and
boiling points than small molecules?
-The intermolecular forces are stronger in large molecules
Why do most covalent substances not conduct
electricity?
-Do not have delocalised electrons or ions
Describe the structure and bonding in graphite.
Each carbon atom is bonded to three others in
hexagonal rings arranged in layers – it has delocalised
electrons and weak forces between the layers
Why can graphite conduct electricity?
-The delocalised electrons can move through the graphite
Explain why graphite is soft.
-Layers are not bonded so can slide over each other
What is graphene?
-One layer of graphite
Give two properties of graphene.
Strong, conducts electricity
What is a fullerene?
-Hollow cage of carbon atoms arranged as a sphere or a
tube
What is a nanotube?
-Hollow cylinder of carbon atoms
Give two properties of nanotubes.
-High tensile strength, conduct electricity
Give three uses of fullerenes.
-Lubricants, drug delivery (spheres), high-tech electronics
What is an ion?
-Atom that has lost or gained electrons
Which kinds of elements form ionic bonds?
-Metals and non-metals
What charges do ions from Groups 1 and 2 form?
Group 1 forms 1+, Group 2 forms 2+
What charges do ions from Groups 6 and 7 form?
Group 6 forms 2−, Group 7 forms 1−
Name the force that holds oppositely charged ions
together.
-Electrostatic force of attraction
Describe the structure of a giant ionic lattice.
-Regular structure of alternating positive and negative
ions, held together by the electrostatic force of
attraction
Why do ionic substances have high melting points?
-Electrostatic force of attraction between positive and
negative ions is strong and requires lots of energy to
break
Why don’t ionic substances conduct electricity when
solid?
-Ions are fixed in position so cannot move, and there
are no delocalised electrons
When can ionic substances conduct electricity?
-When melted or dissolved
Why do ionic substances conduct electricity when
melted or dissolved?
Ions are free to move and carry charge
Describe the structure of a pure metal.
Layers of positive metal ions surrounded by delocalised
electrons
Describe the bonding in a pure metal.
-Strong electrostatic forces of attraction between metal
ions and delocalised electrons
What are four properties of pure metals?
-Malleable, high melting/boiling points, good conductors
of electricity, good conductors of thermal energy
Explain why pure metals are malleable.
-Layers can slide over each other easily
Explain why metals have high melting and boiling
points.
-Electrostatic force of attraction between positive metal
ions and delocalised electrons is strong and requires a
lot of energy to break
Why are metals good conductors of electricity and
of thermal energy?
-Delocalised electrons are free to move through the metal
What is an alloy?
-Mixture of a metal with atoms of another element
Explain why alloys are harder than pure metals.
Different sized atoms disturb the layers, preventing
them from sliding over each other
How big are nanoparticles?
1–100nm
How are nanomaterials different from bulk materials?
-Nanomaterials have a much higher surface area-tovolume ratio
What is the relationship between side length and
surface area-to-volume ratio?
-As side length decreases by a factor of ten, the surface area-to-volume ratio increases by a factor of ten
What are nanoparticles used for?
-Used in healthcare, electronics, cosmetics,
and catalysts
