unit 1 Flashcards
metallic elements within the first 20
Lithium
Beryllium
Sodium
Magnesium
Aluminium
Potassium
Calcium
covalent molecular elements within the first 20
H2
N2
O2
F2
Cl2
P4
S8
carbon in form of fullerene (C60)
covalent network elements within the first 20
Boron
Silicon
Carbon (diamond and graphite)
what is meant by the term covalent radius?
measure of the size of an atom from the nucleus to the outermost electron shell
covalent radius going across a period
decreases
nuclear charge increases
therefore, electrons are pulled closer to the nucleus
covalent radius going down a group
increases
more electron shells so increased shielding
therefore electrons have a weaker pull towards the nucleus
what is meant by the first ionisation energy?
energy required to remove one mole of electrons from one mole of gaseous atoms
what is meant by the second ionisation energy?
energy required to remove the 2nd mole of electrons from one mole of gaseous atoms
ionisation energy going across a period
increases
nuclear charge increases
pull on outer electrons is stronger so it is harder to remove them
ionisation energy going down a group
decreases
more electron shells so increased shielding
therefore electrons have a weaker pull towards the nucleus making it easier to remove them
removing electrons from a full outer shell increased ionisation energy
involves the removal of an electron from a full electron shell
this electron shell is also strongly pulled towards the nucleus compared to the previous shell
what is meant by the term electronegativity?
the strength an atom has for bonded electrons
how to atoms get a delta -/+ charge?
in polar molecules
the atom with the stronger electronegativity pulls the electrons closer given them a delta - charge and the other atom a delta + charge
electronegativity going across a period
increases
nuclear charge increases causing the atom to be smaller
stronger attraction on outer electrons
electronegativity going down a group
decreases
more electron shells so increased shielding
less attraction on outer electrons
why do noble gases not have an electronegativity value?
unreactive/cannot form bonds
intramolecular bonding
strong bonds between atoms in the same molecule
intermolecular bonds
weak bonds between molecules
intermolecular bonds in increasing strength
LDF’s
pd-pd interactions
hydrogen bonding
covalent bonding
two positive nuvelei being held together by their common attraction for the shared pair of electrons
ionic bonding
electrostatic attraction between positive and negative ions forming a lattice
non-polar covalent bonds
forms between atoms with the same electronegativity values
polar covalent bonds
atoms have different electronegativity values so there is an uneven sharing of electrons
what is a dipole?
uneven distribution of electrons
what type of dipole is found in polar molecules?
permanent
describe the bonding continuum?
electronegativity difference
OR ionic character
least - non-polar
middle - polar
high - ionic
how can polar bonds be overall non-polar?
bonds are symmetrically opposed and will cancel out
intermolecular forces (van der Waals) in order of increasing strength
LDF’s
PD-PD interactions
H bonding
where do LDF’s occur?
between all molecules
how are LDF’s formed?
forces of attraction between temporary dipoles and induced dipoles in nearby molecules
how is the strength of an LDF determined?
the more electrons = the stronger it is
where do PD-PD interactions occur?
in polar molecules
where does hydrogen bonding occur?
in bonds where hydrogen is bonded to either Nitrogen, Oxygen or Fluorine
bonding in monatomic
held together by weak LDF’s
what bonds break in a covalent network?
covalent bonds
what bonds are broken in covalent moleculars?
the Van Der Waal force
why when comparing MP we need similar GFMs?
similar LDF strength
bonds in order of decreasing strength
covalent network
ionic
metallic
polar
non-polar
monatomic
explain the structure of ice
H bonding results in an expanded structure that causes the density of ice to be less than that of water at low temperatures
how is viscosity measured?
as the number of H bonds increases, the viscosity increases
what is a reducing agent?
substance that donates electrons
thing being oxidised
what is an oxidising agent?
substance that accepts electrons
thing being reduced
low electronegativity
reducing or oxidising agent?
from ions by losing electrons so act as reducing agents
high electronegativity
reducing or oxidising agent?
form ions by gaining electrons and act as oxidising agents
where can the strongest reducing agents be found?
group 1
top right of the ECS
oxidising agent examples
hydrogen peroxide
dichromate and permanganate ions in acidic solutions
where can the strongest oxidising agents be found?
group 7
bottom left of the ECS
reducing agent examples
carbon monoxide
oxidising agent uses
kill fungi and bacteria
inactivate viruses
breaking down coloured compounds - bleach
