covalent bonding again (same thing) Flashcards
covalent bonds are formed by non metals or metals
mon metals
non metals can share ____ with other ___ ____ atoms to obtain a ___ ______ ____
electrons
non metal
full outer shell
covalent bonds between atoms are very ( weak or strong)
strong
covalently bonded substances may be ____________ or _____________
simple molecular structures
giant covalent structures
shared electrons are called ______ electrons and are found in ____
bonding
pairs
electrons on the ____ shell which are not involved in the covalent bonds are called
non bonding electrons
whats the difference between ionic and covalent bonds
in covalent bonds the electrons are shared between the atoms, they are not transferred (donated or gained) and no ions are formed.
in a covalent bond, is the electrostatic strong or weak between the shared pair of electrons and why
the electrons are negatively charged and the nuclei are positively charged
in covalent bonds, are the electrons in a fixed position
no, they are in constant motion
what does covalent bonding do to the atom
makes it more stable
covalent bonding forms a
molecule
a single covalent bond is shown by
drawing a straight line between them
H-H
Cl-Cl
what is a single covalent bond
when one pair of electrons is shared
what is a double covalent bond
when 2 pairs of electrons are shared
example of an atom that has a double covalent bond
oxygen 0₂
how is a double covalent bond represented
two straight lines between the atom
0=0
What does diatomic mean
it consists of two atoms covalently bonded together
do triple bonds exist
if yes give an example
yes
nitrogen
how is a triple bond represented
N≡N
Three lines between the atoms
what bond is the strongest (double, single or triple)
triple, it would need a lot of energy to break
why is nitrogen so unreactive ( think of bonds)
it has a triple bond which would need huge amounts of energy to break so is a very unreactive gas
covalent substances tend to have what structures
simple molecular like Cl₂ or H₂O
draw a dot and cross for :
Hydrogen
Chlorine
Nitrogen
Oxygen
Hydrogen Chloride
Water
Ammonia
Carbon Dioxide
Methane
Ethane
Ethene
answers on save my exams
what are simple molecular compound made of
a few atoms covalently bonded together
why are simple molecular compounds usually liquids or gases at room temperature
they have low melting and boiling points
and weak electrostatic attractions between the molecules
are simple molecular structures solid at room temp
NO
as a simple molecular compound increases in size, what happens to its melting and boiling points and why
As the molecules increase in size the intermolecular forces also increase as there are more electrons available
what can be said about the conductivity of simple molecular structures
have poor electrical and thermal conductivity
are the covalent bonds strong or weak
strong
how can we show that if size increases, so does melting and boiling points ( what do we use/ graph)
we can use alkanes on a graph
why can simple molecular compounds not conduct electricity
no free or delocalised electrons so cannot carry a charge
simple molecular compounds are ( insulators or conductors)
insulators
example of a use of simple molecular structure
coating on an electrical wire ( insulator)
as the relative molecular mass of a substance increases, what happens to the melting and boiling points
they also increase
why do melting and boiling points increase when relative molecular mass does
there are more electrons in the structure, so there are more intermolecular forces of attraction that need to be overcome when a substance changes state
So larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point
Simple molecular structures are ___ conductors of electricity (even when molten) because (2)
poor
there are NO free ions or electrons to move or carry a charge
- most covalent compounds do not conduct at all in the solid state and so are insulators
-
giant covalent structures are ___ at room temperature
SOLID
GIANT covalent structures have ___ melting and boiling points
high
how are the bonds in a giant covalent structure
very strong
GIANT covalent structures can also be called
giant lattices
All giant covalent structures have high melting points because: (2)
There are strong covalent bonds between atoms
These require lots of energy to overcome
