module 2: electronic configuration Flashcards
what are the rules for assigning oxidation numbers
- O is +2 with F
- O is -1 in a peroxide
- H is -1 with metals
- aluminium = +3 always
- g1 = +1 always
- g2 = +2 always
what is an acid
a species that is a proton donor
what is a base
a species that is a proton acceptor
what is an alkali
a water soluble base
what is a strong acid
an acid that fully dissociates into a solution of H+ ions
what is disproportionation
when one element in a reaction is both oxidised and reduced
in a redox reaction between an acid and a metal what is oxidised/reduced
metal is oxidised => positive metal ion
hydrogen from acid is reduced => hydrogen as an element
acid + metal –>
acid + metal –> metal salt + hydrogen
acid + alkali –>
acid + alkali –> metal salt + water
acid + metal oxide –>
acid + metal oxide –> metal salt + water
acid + metal hydroxide –>
acid + metal hydroxide –> metal salt + water
acid + metal carbonate –>
acid + metal carbonate –> metal salt + water + carbon dioxide
what is an oxidation number
a measure of the number of electrons that an atom uses to bond with the atoms of another element
what does a reduction/increase in oxidation state mean
reduction in os = species was reduced
increase in os = species was oxidised
what are the 2 disproportionation reactions that you need to know?
Cl2(aq) + H2O –> HClO(aq) + HCl(aq)
chlorine is added to water to kill bacteria to make water safe to drink, hydrochloric and chloric acid are formed
Cl2(aq) + 2NaOH(aq) –> NaCl(aq) + NaClO(aq) + H2O(l)
bleach is formed when cold, dilute, aqueous sodium hydroxide and chlorine react at room temperature
what is first ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ atoms
what are the 3 factors that affect ionisation energy
- nuclear charge
- distance from nucelus
- electron shielding
how does ionisation energy change as you go down group 2
it decreases
the number of filled shells increases as you go down a group
so shielding and distance from nucleus increases, making it easier to remove the outermost electron
what is an orbital
a region within an atom that can hold up to two electrons, with opposite spin
outline an s orbital
its spherical
each shell will contain an s orbital
the greater value of n, the greater the s-orbital radius
outline p-orbitals
3D dumb-bell shape
from the 2nd shell onwards, each shell contains 3 p-orbitals
the greater the value of n, the further the p-orbital from the nucleus
how does ionic bonding occur
a type of bonding where one atom loses electrons and one atom gains them
it occurs between a metal and a non-metal, atoms become charged and are attracted to each other
what is covalent bonding
a type of bonding where atoms share electrons with each other
it usually occurs between non-metal atoms, diatomic molecules are formed through covalent bonding
what is metallic bonding
a type of bonding where a sea of free electrons is created
it occurs between metal atoms, electrons become delocalised and more free to move
what are properties of ionic compounds
- solid at room temperature
- high melting and boiling points; strong electrostatic forces of attraction
- soluble
- conducts when molten/in solution
do ionic compounds conduct electricity
only when molten or in solution
they are made of charged particles but electricity is the movement of these, they can move when the substance is a liquid
the ionic lattice dissolves in a polar substance like water
what is a dative covalent bond
a shared electron pair that has been provided by only one of the bonding atoms; the shared pair was originally a lone pair in one of the bonded atoms
why does dative covalent bonding occur
it can be energetically favourable for one species to donate a lone pair to another atom/ion, both species are left with full subshells
properties of simple covalent substances
- low melting and boiling point; weak intermolecular forces don’t need a lot of energy to be broken even though they have strong covalent bonds
- don’t conduct electricity; lack of charged particles
properties of metals
- electrical conductors
charge is carried by delocalised electrons
- high melting and boiling points; strong forces of electrostatic attraction between oppositely charged ions need to be overcome
- insoluble
what is electron pair repulsion theory + what is relative repulsion
bonded electron pairs exert a repulsion onto other repulsion pairs
this causes electron pairs to move as far apart as possible
determining the 3 dimensional shape of the molecule
lonepair-lonepair > lonepair-bondpair > bondpair-bondpair
what are the bond angles in CH4
109.5°
what are the bond angles in NH3
107°
what are the bond angles in H2O
104.5°
there are two bonding pairs and two lone pairs
what is the shape name and bond angle with 4 bonding pairs and no lone pairs
tetrahedral, 109.5°
what is the shape and bond angle with 2 bonding pairs and no lone pairs
linear, 180°
what is the shape name and bond angle with 3 bonding pairs and no lone pairs
trigonal planar, 120°
what is the shape name and bond angles with 5 bonding pairs and no lone pairs
trigonal bipyramidal, 120° and 90°
what is the shape and bond angles with 6 bonding pairs and no lone pairs
octahedral, 90°
what is the shape name and bond angle with 3 bonded pairs and one lone pair
pyramidal, 107°
what is the shape name and bond angle with 2 bonding pairs and 1 or more lone pairs
non-linear, bent, 104.5°
define electronegativity
a measure of an atom’s tendency to attract a bonding pair of electrons in a covalent bond
what are the factors affecting electronegativity
atomic charge
atomic radius
electron shielding
how does electronegativity change across a period and why
nuclear charge increases
atomic radius decreases
electron shielding stays constant
overall increase
how does electronegativity change down group 2
overall decrease
the bonding pair of electrons is increasingly distant from the attraction of the nucleus
what is used to assign values for electronegativity
the Pauling Scale
what makes a molecule polar vs non-polar
it has to be an asymmetrical molecule, the dipoles shouldn’t cancel out each other
symmetrical molecules are non-polar because the dipoles cancel out even though they contain polar bonds
it isn’t dependent on whether or not a molecule contains polar bonds
what are the three most common intermolecular forces, in order of strongest to weakest
hydrogen bonds
permanent dipole-dipole interactions
induced dipole-dipole interactions
what is an induced dipole-dipole interaction
where an instantaneous dipole induces a dipole in another molecule, these attractions can occur between any molecule (even non polar molecules)
because electrons move at very high speeds in orbitals and can lie on one side of an atom at any given point, causing an instantaneous dipole that produces an induced dipole in a neighbouring molecule/atom that is attracted
how does increasing the no. of electrons in a molecule impact the induced dipole-dipole interactions
larger instantaneous and induced dipole –> greater induced dipole interactions and stronger attractive forces between molecules, will require more energy to overcome the forces
permanent dipole-dipole interaction
a weak attractive force between permanent dipoles in neighbouring polar molecules
polar molecules can also have induced dipole-dipole interactions at the same time, leading to even higher boiling points
what is hydrogen bonding
a strong dipole-dipole attraction between an electron deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom (O, N and sometimes F) on a different molecule
what is an oxidising agent vs a reducing agent
a reducing agent gets oxidised
an oxidising agent gets reduced
what are 3 definitions of reduction
gain of electrons
loss of oxygen
gain of hydrogen
how many electrons can each of the first 3 shells hold
shell 1 - 2
shell 2 - 8
shell 3 - 18
why are groups 1 and 2 known as s-block elements
because the highest energy electrons are found in the s subshell
what is a covalent bond
a shared pair of electrons and a strong electrostatic attraction
first ionisation energy equation with an acid
H2SO4 (aq) —> HSO4- + H+
remove a H+
what makes a branched hydrocarbon have a lower boiling point than a straight chain one?
branched has weaker induced and permanent dipole-dipole forces between molecules because the molecules aren’t packed as closely together meaning that there are less surface interactions
how is dative covalent bonding shown in diagrams
using an arrow that points away from the ‘donor atom’
what is the electronic configurations of chromium
Cr is: [Ar] 3d5 4s1 not [Ar] 3d4 4s2
what equation is used when trying to calculate heat energy and units
Q = mc∆T
Heat energy (J) = Mass(of the thing changing temp)(g) × SHC × change in temperature (C)
what determines the order of elements in the periodic table
number of protons
what are the giant covalent structures
boron
carbon
silicon
are intermolecular forces or intramolecular forces stronger?
intramolecular forces are stronger
(a H bond is like a tenth the strength of a covalent bond)
how is percentage uncertainty calculated
% uncertainty = (uncertainty x no. times read) ÷ measured value x 100
what is volumetric analysis
a process that uses the volume and concentration of one chemical reactant (standard solution) to determine the concentration of another, unknown solution
most commonly done via titration
how is a standard solution made
they are made as accurately and precise as possible by using 3 d.p balances and volumetric flasks to minimise measurement uncertainties
- precisely weigh out solid
- add to a small volume of water and pre-dissolve the solid
- transfer to a volumetric flask with a funnel
- rinse the beaker and funnel with distilled water, adding the rinsing to the flask
- make up to the scratch mark with more distilled water, add the slobber and mix the contents
how is a volumetric pipette used in titrations
to measure a known volume of a solution which is added to the conical flask
how is a burette used in titrations
it holds one of the solutions and the tap is opened to release some slowly
what are concordant results
within 0.1cm3 of each other
what is the electronic configuration of copper
Cu is: [Ar] 3d10 4s1 not [Ar] 3d9 4s2
what are ionic compounds made from
a metal and a non-metal
what are covalent compounds made from
2 non-metals
what ions are deflected the most in mass spectrometry
ions with a smaller m/z ratio
what can increase the size of an induced dipole
number of electrons
are double, single or triple bonds harder to break
single are easiest and it gets harder usually!
what are the relative sizes of the cation and anion in an ionic lattice
cation is smaller because it’s lost the electron
anion is bigger because it gains electron
what does a lewis structure of an ion always need
THE OVERALL CHAGRGW!!!!£ 😝😝😝😝😜😜🫵🫵🫵🫵🫵
when going from Q(joules) to delta H neutralisation (kJmol-1) what molar value do you use
moles of water formed
what should you talk about in a question on melting points
intermolecular forces!!
ie.
permanent dipole-dipole
hydrogen bonding
induced dipole-dipole
why is 2nd ionisation energy usually higher
because the proton:e- ratio in a positive ion is greater than before
what can you do when struggling to determine what element has a higher x ionisation energy
write out the electron configurations
what are the units for temp in Q=mcdeltaT
celsius
how do you calculate deltaH from Q
divide Q by the moles of the reactant that isn’t in excess
what will the increase in temp be if the same concentrations of reactant are used, but the volumes are doubled (10deg before) and why
the same! because double the energy will be spread over double the volume
how is a redox equation balanced
use oxidation numbers
1. determine oxidation numbers of every species
2. write half reactions with the oxidation numbers and e- to make up for charge differences
3. make the no. of e- equal and balance
4. use to balance actual
what is the structure and bonding in a metal
giant lattice
what is the structure and bonding in a covalent substance
simple molecular
what is the structure and bonding in an ionic substance
giant lattice
what states are used in ionisation energy equations
gas!!!!
what is the type of compound when a question says that a gas is formed
carbonate and CO2 is being formed
what to discuss when comparing ionisation energies
- sub-shells (state them)
- energy levels eg. 2p is a higher energy level than 2s
- shielding
- nuclear charge
- attraction
