Atomic Structure
Atoms are made from protons, neutrons, and electrons. Protons and neutrons
are known as nucleons.
IMPORTANT!
ADD BITS YOU
Electrons have a negligible mass compared to protons and neutrons which
both have a relative mass of 1. Protons and electrons have equal and opposite
FORGET MOST
magnitudes of charge, 1+. 1-.
MASS NUMBER – Total number of protons and neutrons in the nucleus
ATOMIC NUMBER – The number of protons in the nucleus of an atom.
Ions are formed when atoms lose or gain electrons.
ISOTOPE – An atom of the same element with a different number of neutrons.
Isotopes have the same chemical properties as they have the same electron
configuration as one another. They have different physical properties to one
another as this is due to the variance in mass.
The model of the atom has changed over time due to the increase in
understanding:
- Daltons model; Suggests that atoms are solid spheres and different spheres
make up different elements
- Thomson’s Model; Atoms are a positive charge with negatively charged
particles in them.
- Rutherford’s Model; Small positive nucleus in the centre of the nucleus and
electrons surrounding it, mostly empty space
- Bohr’s Model; Electrons exist in fixed orbitals and these have fixed energy.
RELATIVE ATOMIC MASS- Average mass of an atom of an element on a scale
where 1/12th of C12 is exactly 1.
Steps of mass spectrometer:
- Ionisation:
o Electrospray -> Sample dissolved in a highly volatile solvent and
injected through a hypodermic needle that is attached to the
positive terminal of a high voltage power supply. The particles gain
H+ and the solvent evaporates leaving gaseous positive ions.
o Electron impact -> high energy electrons are fired out of an
electron gun which knocks out electrons from atoms.
- Acceleration: An negatively charged plate attracts electrons towards it
and all ions are accelerated to the same kinetic energy.
- Flight tube: The ions drift through this region with the same speed as they
left the electric field with
- Detection: Ions hit a plate and gain an electron causing a current to flow,
the size of this current can be measured to determine the abundance of
each of the isotopes.
Mass spectrometry can used to identify elements in a sample.
,Electrons move around the nucleus in energy levels. Shells are divided up into
subshells. s,p,d,f. Each sub shell will have a set number of orbitals. S -> 1, p -> 3, d ->
5, f -> 7. Electron configuration can be shown through sub shell notation, arrows in
boxes representing orbitals, and energy level diagrams.
Electrons fill up lowest energy subshells first and full up orbitals singly before pairing
p.
Chromium and copper both have a different electronic configuration in order for
them to be stable.
Cr -> 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Cu ->1s2 2s2 2p6 3s2 3p6 4s1 3d10
The periodic table is split up into blocks based on the outermost subshell that each
element fills in it.
FIRST IONISATION ENERGY – The energy needed to remove 1 electron from each
atom in 1 mole of gaseous atoms to form 1 moles of gaseous 1+ ions.
Factors affecting ionization energy are:
- Nuclear charge; more protons in nucleus means that outermost electrons are
more attracted to the nucleus.
- Distance of outermost electrons from the nucleus; Outermost electrons are
more attracted to the nucleus if the atomic radius is smaller
- Shielding; Outermost electrons are more attracted to the nucleus if there are
fewer inner electron shells.
First ionization energy of magnesium: Mg(g) -> Mg(g)+ + e-
Ionisation energy decreases down group two as there is more electron shielding as
you go down the group as there are more electron shielding, so the outermost
electrons are more attracted to the nucleus and less energy is required to remove
them.
Ionisation energy generally increases across period three due to the increase in
nuclear charge but there is no increase in shielding. There are several exceptions:
- Aluminium is lower than magnesium as a sub shell that is further from the
nucleus is filled so the outermost electron is further from the nucleus
- Sulfur is lower than phosphorous; an electron is being removed from a paired
3p orbital so the electron repulsion means that it is easier to remove the
electron.
Ionisation energy provides evidence for electron shells.
, Amount of Substance
AVOGADROS CONSTANT – The number of atoms in 12g of carbon 12
IMPORTANT!
The avogadros constant is equal to the number of molecules that are in a ADD BITS YOU
mole of any substance.
FORGET MOST
Mass of a substance can be calculated if you know its Mr and the number of
moles you have of it. Mass = Mr * Moles
The number of moles in a solution can also be calculated using the formula n
= cv, where n = number of moles, c = concentration of the solution in moldm-3
and v = volume of the solution in dm3.
The ideal gas equation -> 𝑝𝑉 = 𝑛𝑅𝑇 where p = Pressure in Pa, V = volume in m3,
n = number of moles, R = the ideal gas constant (8.31) and T = temperature in
K
Ionic equations are reaction equations that show how the individual ions
react in a reaction. Only the particles that react are included, meaning that
all ‘spectator ions’ are removed.
MOLAR RATIO – The ratio moles of each reactant and product in a balanced
chemical equation.
State symbols are used in an equation to show what state of matter things are
when they react with one another.
EMPIRICAL FORMULA – The smallest whole number ratio of atoms of each
element present in a compound
MOLECULAR FORMULA – The actual number of atoms of each element that
are present in a molecule.
THEORETICAL YIELD – The mass of products that should be formed in a
chemical reaction assuming no chemicals are lost in the process.
𝑨𝒄𝒕𝒖𝒂𝒍 𝒀𝒊𝒆𝒍𝒅
𝑷𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒚𝒊𝒆𝒍𝒅 = × 𝟏𝟎𝟎
𝑻𝒉𝒆𝒐𝒓𝒆𝒕𝒊𝒄𝒂𝒍 𝒀𝒊𝒆𝒍𝒅
ATOM ECONOMY – A measure of the proportion of reactant atoms that have
become part of the useful product in a reaction
Advantages of a high atom economy are:
- Economic:
o More efficient use of raw materials so less money must be spent
on them
o Less waste to deal with, so less money needs to be spent on
recycling
- Environmental:
o Fewer raw materials used is better for the environment
o Less harmful chemicals are produced as waste which is also
better for the environment
o Processes with higher atom economies tend to be more
sustainable
𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡
𝑎𝑡𝑜𝑚 𝑒𝑐𝑜𝑛𝑜𝑚𝑦 % = × 100
𝑠𝑢𝑚 𝑜𝑓 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠𝑒𝑠 𝑜𝑓 𝑎𝑙𝑙 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠
Atom economy should always be calculated using a balanced equation.
, Bonding
Ions are formed from the electron transfer between two atoms so that they get a IMPORTANT!
full outer shell of electrons. The number of electrons that an atom will lose or gain
can be calculated through use of their group number in the periodic table. An ADD BITS YOU
atom in group 1 for example, will only lose 1 electron from their outer shell of FORGET MOST
electrons to form a stable ion.
Example of compound ions are:
- Ammonium – NH4+
- Carbonate – CO32-
- Hydroxide – OH-
- Nitrate – NO3-
- Sulfate – SO42-
Ionic bonding is the strong electrostatic force of attraction between oppositely
charged positive and negative ions that are held together in a giant ionic lattice.
Positive ions are cations and negative ions are anions.
A giant ionic lattice is a giant regular structure that is made up of the same basic
repeating unit. Ionic compounds can have different shaped structures however
they are all ionic lattices. These ionic lattices are examples of a type of crystal
structure.
Physical properties of ionic compounds :
- Conduct electricity when molten or dissolved in aqueous solution as the
ions are free to move and carry a charge.
- High melting point due to the strong electrostatic forces of attraction that
require a large amount of energy to overcome.
- Soluble in water due to the polar water molecules causing the lattice to
dissociate into ions and these form intermolecular bonds with the polar
water molecules
COVALENT BOND – A shared pair of electrons.
Molecules are formed when two or more atoms bond together. 1, 2 or 3
covalent bonds can form between two atoms.
Compounds made of many individual molecules that are held together by
covalent bonds are called simple covalent compounds. The molecules are
bonded to one another through weak intermolecular forces.
Physical properties of simple molecular compounds:
- Do not conduct electricity as there are no free charged particles to carry
a charge.
- Low melting point due to weak intermolecular forces
- Soluble in water dependant on how polar the molecules are
Atoms are made from protons, neutrons, and electrons. Protons and neutrons
are known as nucleons.
IMPORTANT!
ADD BITS YOU
Electrons have a negligible mass compared to protons and neutrons which
both have a relative mass of 1. Protons and electrons have equal and opposite
FORGET MOST
magnitudes of charge, 1+. 1-.
MASS NUMBER – Total number of protons and neutrons in the nucleus
ATOMIC NUMBER – The number of protons in the nucleus of an atom.
Ions are formed when atoms lose or gain electrons.
ISOTOPE – An atom of the same element with a different number of neutrons.
Isotopes have the same chemical properties as they have the same electron
configuration as one another. They have different physical properties to one
another as this is due to the variance in mass.
The model of the atom has changed over time due to the increase in
understanding:
- Daltons model; Suggests that atoms are solid spheres and different spheres
make up different elements
- Thomson’s Model; Atoms are a positive charge with negatively charged
particles in them.
- Rutherford’s Model; Small positive nucleus in the centre of the nucleus and
electrons surrounding it, mostly empty space
- Bohr’s Model; Electrons exist in fixed orbitals and these have fixed energy.
RELATIVE ATOMIC MASS- Average mass of an atom of an element on a scale
where 1/12th of C12 is exactly 1.
Steps of mass spectrometer:
- Ionisation:
o Electrospray -> Sample dissolved in a highly volatile solvent and
injected through a hypodermic needle that is attached to the
positive terminal of a high voltage power supply. The particles gain
H+ and the solvent evaporates leaving gaseous positive ions.
o Electron impact -> high energy electrons are fired out of an
electron gun which knocks out electrons from atoms.
- Acceleration: An negatively charged plate attracts electrons towards it
and all ions are accelerated to the same kinetic energy.
- Flight tube: The ions drift through this region with the same speed as they
left the electric field with
- Detection: Ions hit a plate and gain an electron causing a current to flow,
the size of this current can be measured to determine the abundance of
each of the isotopes.
Mass spectrometry can used to identify elements in a sample.
,Electrons move around the nucleus in energy levels. Shells are divided up into
subshells. s,p,d,f. Each sub shell will have a set number of orbitals. S -> 1, p -> 3, d ->
5, f -> 7. Electron configuration can be shown through sub shell notation, arrows in
boxes representing orbitals, and energy level diagrams.
Electrons fill up lowest energy subshells first and full up orbitals singly before pairing
p.
Chromium and copper both have a different electronic configuration in order for
them to be stable.
Cr -> 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Cu ->1s2 2s2 2p6 3s2 3p6 4s1 3d10
The periodic table is split up into blocks based on the outermost subshell that each
element fills in it.
FIRST IONISATION ENERGY – The energy needed to remove 1 electron from each
atom in 1 mole of gaseous atoms to form 1 moles of gaseous 1+ ions.
Factors affecting ionization energy are:
- Nuclear charge; more protons in nucleus means that outermost electrons are
more attracted to the nucleus.
- Distance of outermost electrons from the nucleus; Outermost electrons are
more attracted to the nucleus if the atomic radius is smaller
- Shielding; Outermost electrons are more attracted to the nucleus if there are
fewer inner electron shells.
First ionization energy of magnesium: Mg(g) -> Mg(g)+ + e-
Ionisation energy decreases down group two as there is more electron shielding as
you go down the group as there are more electron shielding, so the outermost
electrons are more attracted to the nucleus and less energy is required to remove
them.
Ionisation energy generally increases across period three due to the increase in
nuclear charge but there is no increase in shielding. There are several exceptions:
- Aluminium is lower than magnesium as a sub shell that is further from the
nucleus is filled so the outermost electron is further from the nucleus
- Sulfur is lower than phosphorous; an electron is being removed from a paired
3p orbital so the electron repulsion means that it is easier to remove the
electron.
Ionisation energy provides evidence for electron shells.
, Amount of Substance
AVOGADROS CONSTANT – The number of atoms in 12g of carbon 12
IMPORTANT!
The avogadros constant is equal to the number of molecules that are in a ADD BITS YOU
mole of any substance.
FORGET MOST
Mass of a substance can be calculated if you know its Mr and the number of
moles you have of it. Mass = Mr * Moles
The number of moles in a solution can also be calculated using the formula n
= cv, where n = number of moles, c = concentration of the solution in moldm-3
and v = volume of the solution in dm3.
The ideal gas equation -> 𝑝𝑉 = 𝑛𝑅𝑇 where p = Pressure in Pa, V = volume in m3,
n = number of moles, R = the ideal gas constant (8.31) and T = temperature in
K
Ionic equations are reaction equations that show how the individual ions
react in a reaction. Only the particles that react are included, meaning that
all ‘spectator ions’ are removed.
MOLAR RATIO – The ratio moles of each reactant and product in a balanced
chemical equation.
State symbols are used in an equation to show what state of matter things are
when they react with one another.
EMPIRICAL FORMULA – The smallest whole number ratio of atoms of each
element present in a compound
MOLECULAR FORMULA – The actual number of atoms of each element that
are present in a molecule.
THEORETICAL YIELD – The mass of products that should be formed in a
chemical reaction assuming no chemicals are lost in the process.
𝑨𝒄𝒕𝒖𝒂𝒍 𝒀𝒊𝒆𝒍𝒅
𝑷𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒚𝒊𝒆𝒍𝒅 = × 𝟏𝟎𝟎
𝑻𝒉𝒆𝒐𝒓𝒆𝒕𝒊𝒄𝒂𝒍 𝒀𝒊𝒆𝒍𝒅
ATOM ECONOMY – A measure of the proportion of reactant atoms that have
become part of the useful product in a reaction
Advantages of a high atom economy are:
- Economic:
o More efficient use of raw materials so less money must be spent
on them
o Less waste to deal with, so less money needs to be spent on
recycling
- Environmental:
o Fewer raw materials used is better for the environment
o Less harmful chemicals are produced as waste which is also
better for the environment
o Processes with higher atom economies tend to be more
sustainable
𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡
𝑎𝑡𝑜𝑚 𝑒𝑐𝑜𝑛𝑜𝑚𝑦 % = × 100
𝑠𝑢𝑚 𝑜𝑓 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠𝑒𝑠 𝑜𝑓 𝑎𝑙𝑙 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠
Atom economy should always be calculated using a balanced equation.
, Bonding
Ions are formed from the electron transfer between two atoms so that they get a IMPORTANT!
full outer shell of electrons. The number of electrons that an atom will lose or gain
can be calculated through use of their group number in the periodic table. An ADD BITS YOU
atom in group 1 for example, will only lose 1 electron from their outer shell of FORGET MOST
electrons to form a stable ion.
Example of compound ions are:
- Ammonium – NH4+
- Carbonate – CO32-
- Hydroxide – OH-
- Nitrate – NO3-
- Sulfate – SO42-
Ionic bonding is the strong electrostatic force of attraction between oppositely
charged positive and negative ions that are held together in a giant ionic lattice.
Positive ions are cations and negative ions are anions.
A giant ionic lattice is a giant regular structure that is made up of the same basic
repeating unit. Ionic compounds can have different shaped structures however
they are all ionic lattices. These ionic lattices are examples of a type of crystal
structure.
Physical properties of ionic compounds :
- Conduct electricity when molten or dissolved in aqueous solution as the
ions are free to move and carry a charge.
- High melting point due to the strong electrostatic forces of attraction that
require a large amount of energy to overcome.
- Soluble in water due to the polar water molecules causing the lattice to
dissociate into ions and these form intermolecular bonds with the polar
water molecules
COVALENT BOND – A shared pair of electrons.
Molecules are formed when two or more atoms bond together. 1, 2 or 3
covalent bonds can form between two atoms.
Compounds made of many individual molecules that are held together by
covalent bonds are called simple covalent compounds. The molecules are
bonded to one another through weak intermolecular forces.
Physical properties of simple molecular compounds:
- Do not conduct electricity as there are no free charged particles to carry
a charge.
- Low melting point due to weak intermolecular forces
- Soluble in water dependant on how polar the molecules are
