Chemistry Test 1
Types of chemical bonds
Ionic
Covalent
Metallic
If an atom gains electrons what charge does it have
Negative
Calcium is in group 2 of the periodic table. What happens to a calcium atom when it becomes an ion?
Because calcium is a Group 2 metal, there are 2 electrons in its outer shell.
Calcium atoms remove these 2 electrons to achieve a full outer shell containing 8 electrons, and in doing so become Ca2+ ions.
Ionic Bondings are made up of
Metal + non-metal
Materials with ionic bonds usually
Have high melting points
Only conduct electricity when molten/dissolved
Covalent bonding involves 2 atoms sharing 1 or more pairs of
electrons
If an ion is positive, it has less electrons than
protons
What do atoms have the same amount of
Protons
Electron
Covalent bonds are made up of
Non-metals only
Metallic bonds are made up of
Metals only
why can't ionic compunds carry an electric current
the ions are fixed in place
the properties of covalent bonds are
occurs between two non-metals
the electrons are shared
they do not involved charged particles
the properties of ionic bonds are
involves charged particles
occurs between metal and non-metal atoms
electrons are lost or gained / transferred
covalent bonds do not conduct electricity due to
mobile charge carriers (e.g delocalised electrons or ions)
why does propane have a low boiling point
the intermolecular forces are weak
all bonds are aiming for
a full outer shell of electrons for stability
the properties of metallic bonds are
there is a sea of delocalised electrons
involves an electrostatic force
can conduct electricity
surface area =
height * width * n(sides)
volume =
base * height * width
are ionic and covalent bonds made up of metals and non-metals
no ionic takes a mix
with Mg3- Cl2+ what can you do to balance them
swap the numbers around e.g Mg2Cl3
what is the big ionic compound of sodium and chlorine atoms called
a giant ionic lattace
what is needed for the ionic compound of sodium chloride to conduct electricity
it needs to be molten or dissolved because the charged ions are attracted to the water ions
they also need to be mobile and free moving
why does potassium chloride have a high melting point
the electrostatic force of attraction between the ions is very strong and require a lot of energy to break
one pair of shared electrons is equal to
one covalent bond
two ways to indicate a covalent bond
H-H a solid line and a dot and cross diagram
properties of SMALL covalent molecules
do not conduct electricity (delocalised electrons)
low boiling point (intermolecular forces)
also the covalent bonds do not break
properties of diamond
high boiling/melting point
doesn't conduct electricity
and is hard
it forms 4 bonds
properties of graphite
high boiling/melting point
conducts electricity
is soft
it forms 3 bonds
why is diamond hard
because the carbon atoms are held strongly together with strong covalent bonds
why is graphite soft
because it is made up of layers of carbon atoms that slide over eachover
why can graphite conduct electricity and diamond can not
because they have delocalised electrons that slide over eachover
what can you use graphene for
anything to do with electricity like a wire
properties of graphene
made from a single layer of graphite
high melting point
it is strong
can conduct electricity
what can buckminister fullerenes be used for
for drug delivery into the body
what can carbon nanotubes be used for
what can graphite be used for
lubricants
what type of shape do fullerenes have
hollow/spherical
why are alloys harder than pure metals
a greater force is required for the layers to slide over each other
properties of carbon nanotubes
high elasticity high thermal conductivity low density
why can anything conduct electricity
DELOCALISED ELECTRONS
an alloy is a metal which
has different types/sizes of atoms
what if something has strong covalent bond
often form molecules, with low melting and boiling points, such as hydrogen and water
what is difference between an ionic and covalent bond
In ionic bonding, one atom donates electrons to the other In covalent bonding, the two atoms share electrons