T2 bonding, structure and the properties of matter Flashcards
what is ionic bonding
electrostatic attraction between positive and negative ions
relatively strong attraction
how are ionic compounds held together
in a giant lattice
regular structure that extends in all directions in a substance
electrostatic attraction between positive and negative ions holds the structure together
state properties of ionic substances
high melting and boiling points (strong electrostatic forces between oppositely charged ions)
don’t conduct electricity when solid (ions in fixed positions)
conduct when molten or dissolved in water - ions are free to move
give 5 examples of positive and negative ions
what is important when working out a formula of an ionic compound
P: Na+ Mg2+ Al3+ Ca2+ Rb+
N: Cl- Br- SO2-4 No-3 OH-
ionic compounds are electrically neutral
how are ionic compounds formed?
reaction of a metal with a non-metal
electron transfer occurs - metal gives away its outer shell electrons to non-metal
what is a covalent bond
shared pair of electrons between 2 atoms
describe the structure and properties of simple molecular covalent substances
don’t conduct electricity (no ions)
small molecules
weak intermolecular forces
low melting and boiling points
how do intermolecular forces change as the mass/size of the molecule increases
increase
causes melting/boiling points to increase as well (more energy needed to overcome these forces)
what are polymers? What are thermosoftening polymers?
very large molecules with atoms linked by covalent bonds
special type of polymers, melt/soften when heated, no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature, forces are overcome with heating - polymer melts
what are giant covalent substances
give examples
solids, atoms covalently bonded together in a giant lattice
high melting/boiling points - strong covalent bonds
mostly don’t conduct electricity
diamond, graphite, silicon dioxide
name the allotropes of carbon
diamond fullerenes graphite nanotubes graphene
describe and explain diamond
four, strong covalent bonds for each carbon atom
very hard, strong bonds
very high melting point
doesn’t conduct
describe and explain graphite
three covalent bonds for each carbon atom
layers of hexagonal rings
high melting points
layers free to slide as weak intermolecular forces between layers,
soft, can be used as lubricant
conduct thermal and electricity due to one delocalised electron per each carbon atom
describe and explain fullerenes
hollow shaped molecules
based on hexagonal rings but may have 5/7 carbon rings
C60 has spherical shape, simple molecular structure (buckminsterfullerene)
describe and explain nanotubes
cylindrical fullerene with length to diameter ratio
high tensile strength (strong bonds)
conductivity (deloc electrons)