Chemistry: Summary
Categories of matter: pure substance and mixtures
Pure substance: made of a single chemical species
Chemical species: can be an element, a molecule or a compound
Single particles of a pure substance are held together by chemical bonds called intramolecular bonds (including covalent, ionic and metallic bonds)
All pure substances are homogenous (uniform)
Mixtures are any combination of more than one pure substance
Mixtures can be separated by a physical process as they aren’t chemically bonded
Categories of mixtures: homogenous and heterogenous
Homogenous mixtures are uniformly mixed
Any solution of a dissolved solute in a solvent is a homogenous mixture
Heterogenous mixtures are not uniformly mixed
Sieving: particle size
Filtration: solid substance, liquid substance, therefore particle size
Vaporisation: liquid has a much lower boiling point
Distillation: big difference in boiling points
Fractional distillation: significant but small difference in boiling points
Sedimentation and decantation: density
Separating funnel: immiscible liquids; different densities
Adding a solvent then filtering: one substance is soluble in the chosen solvent, while the others are insoluble
%weight = mass of component/total mass of mixture x 100
IUPAC naming conventions for ionic compounds: positive ion (cation) first, negative ion (anion) second, anions ending changed to ‘ide’
IUPAC naming conventions for covalent compounds (simple inorganic): least electromagnetic element first, the most electromagnetic element second, second element ending is changed to ‘ide’ and both elements need a Greek prefix
Periodicity: relationship between elements’ physical and chemical properties and their position in the periodic table
Thermal physical properties: boiling point, melting point, heat capacity, heat conductivity
Mechanical physical properties: hardness, viscosity, density, ductility, brittleness
Optical physical properties: colour, transparency, reflectivity, refractivity, absorption, lustre
Electrical physical properties: electrical conductivity, resistance, electric charge
Chemical properties: acidity and basicity, combustibility, ability to oxidise or reduce
Periodic Law: the properties of the elements are periodic functions of their atomic number
Properties of metals: shiny, malleable, good conductors of heat and electricity
Properties of non-metals: appear dull, poor conductors of heat and electricity
Properties of metalloids: conduct heat and electricity moderately well, possess some properties of metals and non-metals
Number of protons defines an element
Mass number = protons + neutrons
Isotope defined by = number of neutrons
Radioactive decay is spontaneous and doesn’t require an input of energy to occur
In nuclear reactions, the nucleus gains stability by undergoing a change of some kind
Radioisotope = an isotope of an element that is unstable and undergoes radioactive decay
Isotope notation = mass number → 12 C
atomic number → 6
All elements with an atomic number greater than 83 are unstable because the nucleus is too large and will decay regardless of the neutron to proton ratio
Quantum mechanics = all matter can be described as both a wave and a particle
Electrons are so small the effects of quantum mechanics are significant
The smaller the object the more its wave-like characteristics come into play
Two qualities of waves that affect the arrangement of electrons: constructive and deconstructive interference which causes electrons to affect the other electrons around them and that waves are stretched out over space from their peak to their trough, which means the exact position of the electron is unknown
Highest probability of an electron = at the peak of the wave
Erwin Schrodinger = developed mathematical equation that uses the wave-like characteristics of electrons to determine where an atom’s electrons are most likely to be
Energy levels = orbitals
Groups of orbitals = shells
Orbitals come in many shapes
Energy levels of electrons can be directed observed by measuring the wavelength of the photons they emit when excited
Electron shells subdivided into electron orbitals
Each orbital only contains 2 electrons
First shell = 1 s orbital
Second shell = 1 s orbital, 3 p orbitals
Third shell = 1 s orbital, 3 p orbitals, 5 d orbitals
Fourth shell = 1 s orbital, 3 p orbitals, 5 d orbitals, 7 f orbitals
Shells referred to as the principle energy level (n)
Hund’s rule: states that for an orbital group also called sublevel (like 2p) electrons will fill all orbitals with a single electron before a second electron can be added
Writing spdf notation: -
ordered left to right
shell number first, orbital type second
number of electrons are represented in superscript after the orbital group (sublevel) eg. 2p^2
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 7s, 5f, 6d, 7p
Using isotopic composition to calculate relative atomic mass: multiply each percentage by the mass number, add them together, divide by 100
Alpha particles: relatively heavy, positively charged, can be stopped by a piece of paper
Beta particles: much lighter, negatively charged, can pass through paper and 0.5mm sheet of aluminium, stopped by 0.5mm sheet of lead
Gamma rays: no charge, extremely penetrating, stopped by 5cm of lead or15cm of concrete
Alpha particles: are helium nuclei (2 protons and 2 neutrons stuck together)
Beta particles: are electrons
Gamma rays: are a type of electromagnetic radiation
d
1mol = 6.022x10^23 particles
6.022x10^23 = Avogadro’s number
Number of particles = mols x Avogadro’s number
mol=m/Mm
Percent composition% = mass of element/mass of compound x 100
Empirical formula
Limiting reagent
j
Enthalpy =
Entropy =
Gibbs free energy =
Categories of matter: pure substance and mixtures
Pure substance: made of a single chemical species
Chemical species: can be an element, a molecule or a compound
Single particles of a pure substance are held together by chemical bonds called intramolecular bonds (including covalent, ionic and metallic bonds)
All pure substances are homogenous (uniform)
Mixtures are any combination of more than one pure substance
Mixtures can be separated by a physical process as they aren’t chemically bonded
Categories of mixtures: homogenous and heterogenous
Homogenous mixtures are uniformly mixed
Any solution of a dissolved solute in a solvent is a homogenous mixture
Heterogenous mixtures are not uniformly mixed
Sieving: particle size
Filtration: solid substance, liquid substance, therefore particle size
Vaporisation: liquid has a much lower boiling point
Distillation: big difference in boiling points
Fractional distillation: significant but small difference in boiling points
Sedimentation and decantation: density
Separating funnel: immiscible liquids; different densities
Adding a solvent then filtering: one substance is soluble in the chosen solvent, while the others are insoluble
%weight = mass of component/total mass of mixture x 100
IUPAC naming conventions for ionic compounds: positive ion (cation) first, negative ion (anion) second, anions ending changed to ‘ide’
IUPAC naming conventions for covalent compounds (simple inorganic): least electromagnetic element first, the most electromagnetic element second, second element ending is changed to ‘ide’ and both elements need a Greek prefix
Periodicity: relationship between elements’ physical and chemical properties and their position in the periodic table
Thermal physical properties: boiling point, melting point, heat capacity, heat conductivity
Mechanical physical properties: hardness, viscosity, density, ductility, brittleness
Optical physical properties: colour, transparency, reflectivity, refractivity, absorption, lustre
Electrical physical properties: electrical conductivity, resistance, electric charge
Chemical properties: acidity and basicity, combustibility, ability to oxidise or reduce
Periodic Law: the properties of the elements are periodic functions of their atomic number
Properties of metals: shiny, malleable, good conductors of heat and electricity
Properties of non-metals: appear dull, poor conductors of heat and electricity
Properties of metalloids: conduct heat and electricity moderately well, possess some properties of metals and non-metals
Number of protons defines an element
Mass number = protons + neutrons
Isotope defined by = number of neutrons
Radioactive decay is spontaneous and doesn’t require an input of energy to occur
In nuclear reactions, the nucleus gains stability by undergoing a change of some kind
Radioisotope = an isotope of an element that is unstable and undergoes radioactive decay
Isotope notation = mass number → 12 C
atomic number → 6
All elements with an atomic number greater than 83 are unstable because the nucleus is too large and will decay regardless of the neutron to proton ratio
Quantum mechanics = all matter can be described as both a wave and a particle
Electrons are so small the effects of quantum mechanics are significant
The smaller the object the more its wave-like characteristics come into play
Two qualities of waves that affect the arrangement of electrons: constructive and deconstructive interference which causes electrons to affect the other electrons around them and that waves are stretched out over space from their peak to their trough, which means the exact position of the electron is unknown
Highest probability of an electron = at the peak of the wave
Erwin Schrodinger = developed mathematical equation that uses the wave-like characteristics of electrons to determine where an atom’s electrons are most likely to be
Energy levels = orbitals
Groups of orbitals = shells
Orbitals come in many shapes
Energy levels of electrons can be directed observed by measuring the wavelength of the photons they emit when excited
Electron shells subdivided into electron orbitals
Each orbital only contains 2 electrons
First shell = 1 s orbital
Second shell = 1 s orbital, 3 p orbitals
Third shell = 1 s orbital, 3 p orbitals, 5 d orbitals
Fourth shell = 1 s orbital, 3 p orbitals, 5 d orbitals, 7 f orbitals
Shells referred to as the principle energy level (n)
Hund’s rule: states that for an orbital group also called sublevel (like 2p) electrons will fill all orbitals with a single electron before a second electron can be added
Writing spdf notation: -
ordered left to right
shell number first, orbital type second
number of electrons are represented in superscript after the orbital group (sublevel) eg. 2p^2
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 7s, 5f, 6d, 7p
Using isotopic composition to calculate relative atomic mass: multiply each percentage by the mass number, add them together, divide by 100
Alpha particles: relatively heavy, positively charged, can be stopped by a piece of paper
Beta particles: much lighter, negatively charged, can pass through paper and 0.5mm sheet of aluminium, stopped by 0.5mm sheet of lead
Gamma rays: no charge, extremely penetrating, stopped by 5cm of lead or15cm of concrete
Alpha particles: are helium nuclei (2 protons and 2 neutrons stuck together)
Beta particles: are electrons
Gamma rays: are a type of electromagnetic radiation
d
1mol = 6.022x10^23 particles
6.022x10^23 = Avogadro’s number
Number of particles = mols x Avogadro’s number
mol=m/Mm
Percent composition% = mass of element/mass of compound x 100
Empirical formula
Limiting reagent
j
Enthalpy =
Entropy =
Gibbs free energy =