3.1.3 Bonding Flashcards
What is electronegativity
The ability of an atom to attract the pair of electrons in a covalent bond.
What 3 factors do electronegativity depend on
size of positive charge in the nucleus
Atomic radius - the closer the bonding pair to the nucleus
shielding - greater shielding, lower electronegativity
What forces of attraction are in ionic bonds
Electrostatic forces of attraction
Ionic bond is made form a
Metal and non-metal
Why do atoms react
To achieve electron configuration of a Nobel gas
Full outer shell of electrons
How are electrons transferred between non-metal and metal in ionic bond + charges
Metal loses electrons to form a positive ion
Non-metals gains electrons to form a negative ion
How are the ions arranged in an ionic bond
A giant lattice structure
Shapes of molecules
2 bond
3 bond
4 bond
5 bond
6 bond
Linear
Triangular planar
Tetrahedral
Trigonal biprymadial
Octahedral
Formula of ammonium
NH4 +
Formula of Carbonate ion
CO3 -2
Formula hydroxide ion
OH-
Formula nitrate ion
NO3 -
Formula sulphate ion
SO4 -2
Ionic compounds - electrical conductivity
Only when molten or dissolved not solid
The ions are held in place by electrostatic forces of attraction and are not free to move and carry charge
Ionic compound - Melting point
High melting point
The giant ionic lattices are held together by strong electrostatic forces of attraction which act in all directions
Ionic compounds - solubility
Tend to be soluable in water.
Water molecules are polar overcomes electron static forces of attraction
Pulls ions away from lattice and dissolves them
Angles in linear molecule
180
Angle in Trigonal planar
120
Angles in Tetrahedral
109.5
Angles in Trigonal biprymidial
90
120
Angles in octahedral
90
In a covalent bond electrons are….
Shared
In simple covalent molecules what determines the property of the molecule
Intermolecular forces
What is expansion of the octet rule
Usually period 3
Can have more than 8 electrons on outer shell
why do simple covalent compounds have low melting and boiling points
Low
strong covalent bonds between atoms in a molecule
weak intermolecular forces of attraction between molecules
which determine their properties
giant covalent is also known as
macromolecular
graphite structure
sheets of flat hexagons
3 bonds to each carbon
delocalised electrons between layer
properties of graphite
lubricant- weak bonds between layers mean they can slide over each other
conductive - delocalised electrons are free to move and carry a charge.
low density- layers are far apart can be used in sports equipment
structure diamond
carbon bonded to 4 other carbons
crystal lattice structure
properties diamond
cant conduct electricity- no free electrons to move and carry a charge
high melting point- strong covalent bonds, lots of energy to overcome
good thermal conductor - vibrations easily travel through the stiff lattice
give an example of each type of molecule
Ionic
Metallic
Simple molecular
Macromolecular x2
ionic - sodium chloride
metallic - magnesium
simple molecular-iodine
macromolecular - diamond, graphite
Positive ions are sometimes called
cations.
Negative ions are sometimes called
anion
what is a dative covalent bond?
where one atom provides both electrons in shared pair
how is a dative covalent bond shown on a diagram
(From which atom to which)
the arrow points away from the atom that has provided the electrons
what 2 conditions must there be for a dative covalent bond to occur
1 atom has a lone pair of electrons
the other doesn’t have any electrons to share
a dative covalent bond is same or different to a ‘normal’ covalent bond
same
what is metallic bonding + bonding?
a lattice of positively charged ions surrounded by a ‘sea’ of delocalised electrons. This produces a very strong electrostatic force of attraction between these oppositely charged particles.
which have greater repulsion loan pairs or bonding pairs
loan pairs
how much do loan pairs reduce a bonding angle
2.5 degrees
does a loan pair becoming a dative covalent bond have any effect on the angle degree
no the angles would act the exact same as if they were all covalent bonds
electron negativity increases as you move ( in general)
to the top-right of the periodic table (excluding nobel gases)
opposite charges on a polar molecule can only cancel if
they are opposite e.g. linear molecule
or equal charges act in all directions
3 types of intermolecular forces
Van Der Waals forces
permanent dipole-dipole interations
hydrogen bonds
Van Der Waals strength
weak and easily broken
How do van der waals occur
Random movement of electrons in one molecule creates a dipole
Induces a dipole in a neighbouring molecule
These temporary dipoles attract
the strength of van der Waals depends on the
number of electrons
which molecules can experience permanent dipole-dipole forces
only molecules with a permanent dipole e.g. water
the strength of a permanent dipole-dipole interaction decreases as
the electronegativity decreases
which is the strongest intermolecular force
hydrogen bonds
what are the two conditions for hydrogen bonding
hydrogen atom bonded to a strongly electronegative element
the electronegative atom must have at least 1 pair of electrons
which 3 elements for hydrogen bonds
oxygen, fluorine, nitrogen
why is ice less dense than water
molecules arranged in an ordered structure
stabilised by a network of hydrogen bonds
molecules are further apart than in liquid
so ice is less dense
suggest why the electronegativity of the elements increases from lithium to fluorine
increased number of protons
same shielding
2 bonding pairs name
Linear
2 bonding 1 lone
Bent / v-shaped
3 bonding pairs
Trigonal planar
4 bonding pairs
Tetrahedral
3 bond 1 loan
Trigonal pyramidal
5 bond
Trigonal biprymidal
4 bond 1 loan
See saw
3 bond 2 loan
T-shape
6 bond
Octahedral
5 bond 1 loan
Square pryramid
4 bond 2 loan
Square planar
Explain how a permanent dipole-dipole forces arise between hydrogen and chlorine molecules
Large difference in electronegativity leads to bond polarity
The chlorine has a § - charge and the hydrogen has a §+ charge THERE IS AN ATTRACTION BETWEEN THE §+ AND §- CHARGES
§ - means slight
Which type of structure has the intermolecular forces hydrogen bonding dipole-dipole etc
Simple molecular covalent
If these are not in the question then talk about ionic, metallic, covalent bonding instead refer to Spring CAT q2) This is very important
Metal + water
E.g. Sodium + water
Metal hydroxide + hydrogen
Na + H20 —> NaOH + 1/2H2
ALWAYS BALANCE
Formula phosphate ion
PO4 -3
Formula hydrogencarbonate
HCO3 -
Ammonia formula
NH3
Acid + metal hydroxide =
Salt + water
How many loan pairs does oxygen have when drawing hydrogen bonding
2
Metal + steam
Metal oxide and hydrogen
3 bond 1 loan bond angle
107
