what is covalent bonding?
attraction between the shared pair of negative electrons and the positive nuclei either side of it
when does covalent bonding occur?
occurs between two non-metals (groups 4,5,6,7)
occurs in solids, liquids and gases (at room temperature)
do covalent bonds conduct electricity and why
Electrons are shared to complete the outer shell
they can’t move therefore doesn’t conduct electricity
how are covalent bonds represented?
with dot and cross diagrams
usually only draw outside shells but unless this is specified it is safer to draw all the shells
what are the bonds between hydrogen atoms
very strong covalent bonds
what do molecules have?
a certain fixed number of particles
what are hydrogen molecules
(contains two molecules)
what is released when bonds are formed
makes things involved more stable
the more bonds and atom can form, the more energy released, the more stable the bond becomes
if hydrogen atom bonds with another hydrogen atom is it less or more stable
when hydrogen and chlorine bond together what molecule do they form
a hydrogen chloride molecule
what type of bond is formed in a hydrogen chloride molecule and what is its diagram
Chlorine has one unpaired electron on outer shell
Hydrogen has one unpaired electron on outer shell
Both atoms bond together and form a covalent bond
what is the significance of noble gas structures
ehen atoms bond covalently, they often produce outer electronic structures the same as noble gases
there are also lots of examples that look nothing like noble gas structures
what is the symbol for a chlorine molecule
what bond is formed in a chlorine molecule and what is its diagram
a covalent bond
each chlorine has an unpaired electron which is shared between the two chlorine atoms
what type of bond do each methane, ammonia and water form
what is the sybol and diagram for methane
symbol = CH4
the carbon atom has four unpaired electrons
they share one electron from four hydrogen atoms
what is they symbol and diagram for ammonia
the nitrogen atoms has three unpaired electrons
they share one electron from three hydrogen atoms
symbol = NH3
what is the symbol and diagram for water?
symbol = H2O
there are two unpaired electrons on the oxygen atom
they bond with two hydrogen atomssymbol = H2O
what bonding is similar to that of methane and what is different?
there is a carbon-carbon bond also
what is the symbol and diagram for ethane?
symbol = C2H6
how many electrons are shared by each atom in single covalent bonding?
how many electrons are shared by each atom in double covalent bonding?
how many electrons are shared by each atoms in triple covalent bonding?
what type of covalent bonding is formed in carbon dioxide and what is its diagram
what type of covalent bonding in nitrogen and what is its diagram
what is special about the structure of sodium hydroxide?
what is its diagram?
you have Na (a metal) and OH (a non-metal) - this makes it ionic
however, the O and H are both non-metals and that makes it covalent
what two types of structures are there in covalent bonding?
what type of bonding is simple molecular
what state of matter do simple molecular substances tend to be?
gases and liquids
how many atoms are bonded together in simple molecular structures
2 or 3 atoms bonded together
how are the atoms in simple molecular substances attracted to each other
attracted to each other through intermolecular force
this is a weak attractive force between two or more molecules
do simple molecular substances have high or low melting and boiling points
do simple molecular substances conduct electricity and why
do not conduct electricity
molecules don’t have any overall electrical charge
there are no electrons that can move from molecule to molecule
do simple molecular substances tend to be soluble or insoluble in water and why?
insoluble (unless they react with it)
due to their size, water molecules have stronger intermolecular attractions between them than you might think
attractions need to be broken for a substance to dissolve so that the dissolving molecules can fit between them
any new attractions between water molecules and the covalent molecules are not usually big enough to make up for this
are simple molecular substances often organic solvents or not and why
intermolecular attractions between the two different types of molecule are much the same as in the pure substances
in water, how do you break the intermolecular forces?
does iodine crystal form a simple molecular structure or a giant covalent lattice?
what does its formation look like?
does water form a simple molecular structure or a giant covalent lattice?
what does its formation look like?
what state of matter are giant covalent structures?
are there intermolecular forces in giant covalent structures? why?
only strong covalent bonds which need lots of energy to break
what are some common properties of giant covalent structures?
Very high melting points and boiling points
Solid, crystalline, hard
Do not conduct electricity
what does the giant covalent lattice of silicon dioxide (sand) SiO2 look like?
does diamond form a simple molecular structure or a giant covalent structure?
giant covalent structure
what is diamonds relationship with carbon?
it is a pure form of carbon
what is the structure of diamond?
each carbon atom has four unpaired electrons on its outer shell
each carbon atoms bonds strongly to four other carbon atoms and each carbon forms four covalent bonds
tetrahedral arrangement which continues on and on in three dimensions
is diamond a molecule? why?
not a molecule because atoms joined up in a real diamond is completely variable (depends on size of crystal)
molecules always contain a fixed number of atoms joined by covalent bonds
is graphite a giant covalent structure or a simple molecular structure?
is graphite a form of carbon?
what is the structure of graphite like
3-D lattice structure
has a layer structure
layers slide easily over each other
why is graphite soft with a slimy feel?
layers easily slide over each other
mixed with clay to make pencils
pure graphite is used as dry lubricant
why does graphite have a high melting point, boiling point and is soluble in any solvents
to melt or dissolve graphite you need to break the whole structure, including the covalent bonds, not just the layers
very large amounts of energy needed as bonds are very strong
why is graphite less dense than diamond?
the layers in graphite are relatively far apart
distance between graphite layers is more than twice the distance between atoms in each layer
graphite cyrstal contains a lot of water space, whereas there is none in a diamond crystal
why does graphite conduct electricity?
each carbon atom is only joined to three others
one electron drops between the layers and becomes delocalised
this electron is free to move around the layer
what are intermolecular forces
forces of attractions between separate molecules
are intermolecular bonds are weaker/stronger than ionic or covalent bonds
they vary in strength from substance to substance
how do intermolecular forces work?
the slightly positive end of one molecule attracts the slightly negative end of a neighbouring molecule
what will heating do to intermolecular forces?
will supply energy to break these intermolecular attractions
causes the substance to either melt or boil
doesn’t take much heat energy to break intermolecular attractions
what does melting do to intermolecular forces?
some but not all intermolecular forces are broken
what does boiling do to intermolecular forces?
the attractions are completely disrupted and the molecules become free to move around as a gas
do melting or boiling break the covalent bonds?
break intermolecular forces not the covalent bonds
where do intramolecular forces occur?
occurs in both simple molecular and giant covalent bonds
inside the molecules, attraction between atoms
what is the diagram for F2
what is the diagram for H2S
what is the diagram for CH4
what is the diagram for PH3
what is the diagram for SiCl4
what is the diagram for C2H6
what is the difference between simple molecular substances and giant covelant structures?