Elements Of Life Flashcards
Describe Dalton’s model of the atom
Solid spheres, where different spheres were different elements
Describe and give evidence for Thompson’s atomic model
Plum pudding model, negative raisin electrons and positive pudding
Charge and mass measurements proved existence of smaller negative particles - electrons
Describe and give evidence for Rutherford’s atomic model
Model of tiny, dense, positive nucleus and cloud of negative electrons around (empty space in between)
Geiger-Marsden experiment, alpha particles fired at gold sheet, most went through but some deflected
Describe and give evidence for Bohr’s atomic model
Electrons arranged in (quantised) energy levels around nucleus
Atomic emission/absorption spectra - lines are shown rather than whole spectrum - levels must be present
Define atomic number
Number of protons in nucleus of an atom
Define mass number
Total number of protons and neutrons in atomic nucleus
Define relative atomic mass
Mean atomic mass compared to 1/12th the mass of a C12 atom
Define relative molecular mass
Average molecular mass compared to 1/12th of a C12 atom
Define relative isotopic mass
Mass of a specific isotope compared to 1/12th of a C12 atom
Define a mole
Amount of a substance that contains same number of particles as 12g of C12 (6.02 x 10^23 particles)
Define ionic equation
An equation that omits spectator ions
Formula for percentage yield
Percentage yield = actual yield / theoretical yield x 100
Formula for percentage composition my mass
Mass of desired substance / mass of mixture x 100
How is a standard solution prepared from a conc solution?
C1V1 = C2V2 is used to calculate measurements
Calculated volume of conc solution added to volumetric flask
Distilled water added to bro mg solution up to line
What shapes are s and p orbitals?
s - spherical
p - dumbbell
Define orbital
Regions of space around an atom where electrons are most likely to be found (contain max 2 electrons)
Describe tendencies of electrons as they fill orbitals
Lazy + antisocial
Lowest energy orbitals first
One in each orbital if possible
Why does the 4s orbital fill before 3d orbital?
4s at lower energy level than 3d
What is fusion?
Two lighter nuclei collide, and combine to form a heavier nucleus (and release energy)
Conditions for fusion
Very high temp and pressure
What is covalent bonding?
Electron pair is shared between 2 atoms.
Strong bond due to strong electrostatic attraction.
Why do giant covalent lattices have greater melting point than simple covalent molecules? (Give examples for each)
Covalent bonds in lattice much stronger than intermolecular bonds between simple molecules
Lattice - diamond, silicon dioxide
Simple - oxygen, carbon dioxide
Why are ionic substances only conductive when dissolved?
Free movement of ions to carry charge
Why do covalent and ionic lattices have high bp?
Both have strong bonds to many atoms, so lots of (heat) energy needed to break many strong bonds
Linear bond angle + conditions
180°, two bonded electron groups
Triangular planar bond angle + conditions
120° and 3 bonded electron groups
Bent bond angle + conditions
104.5° and 2 bonded groups, 2 lone pairs
Trigonal pyramidal bond angle + conditions
107° and 3 bonded groups, 1 lone pair
Tetrahedral bond angle + conditions
109.5° and 4 bonding groups
Octahedral bond angle + conditions
90° and 6 bonded groups
Explain lone pair repulsion theory
Electron pairs repel (same negative charge)
To reduce repulsion, they move as far from each other as possible
Lone pairs repel more than bonded pairs, causing diff bond angles/shapes
What is first ionisation enthalpy
The enthalpy change from the removal of 1 mol electrons from 1 mol of gaseous atoms
What’s does group number mean in periodic table
Number of electrons in atoms outer shell
What does period mean in periodic table
Number of electron shells in the atom
Why does first ionisation enthalpy increase as you move across a period
More attraction between outer shell electrons and positive nucleus, due to increase in protons, so more energy needed to remove them
Nitrate ion formula
NO3 -
Sulphate ion formula
SO4 2-
Carbonate ion formula
CO3 2-
Hydroxide ion formula
OH -
Ammonium ion formula
NH4 +
Hydrogencarbonate ion formula
HCO3 -
Charge of most transition metals in period 4
2+
Why does first ionisation enthalpy decrease down a group
More shielding (more electrons between nucleus and outer shell)
Longer distance between nucleus and outer shell
Even though protons have increased, attraction between nucleus and outer shell is lower so less energy needed to remove
How do the charge densities of group 2 ions affect the thermal stability of their carbonates?
Higher charge density - more polarising - distorts carbonate ion more - lower thermal stability (break down at lower temps)
How to test for Fe 2+ ions
Add OH -
Green precipitate forms
How to test for Fe 3+ ions
Add OH -
Orange precipitate forms
How to test for Cu 2+ ions
Add OH -
Blue precipitate forms
How to test for NH4 + ions
Add NaOH (aq) to tube with NH4 +
Heat
Vapours from tube will turn damp red litmus paper blue
How to test for Al 3+ ions
Add OH -
White precipitate forms
How to test for halide ions
Dissolve substance in HNO3
Add AgNO3
Ag+(aq) + X-(aq) ➡️ AgX(s) (Where X is halide)
Silver chloride is white precipitate (dissolves in dilute ammonia)
Silver bromide is cream precipitate (dissolves in conc ammonia)
Silver iodide is yellow precipitate (doesn’t dissolve)
How to test for SO4 2- ions
Add Ba 2+ ions
White precipitate forms
How to test for CO3 2- ions
Add dilute nitric acid
Effervescence occurs
OR
Add dilute HCl
Bubble gas (CO2) through lime water, which will turn cloudy
How to test for Li+ , Na+ , K+ and Ca+ ions
Use flame tests
Give flame test colours
Sodium - orange
Calcium - brick red
Lithium - crimson
Potassium - lilac
Barium - apple green
Copper - blue-green
How to test for Pb 2+ ions
Add OH- ions,
White precipitate forms
adding more OH- ions causes precipitate to dissolve
What is an acid
Species that donates H+ ions
What is a base
Species that accepts H+ ions in solution (releases OH- ions)
What is an alkali
A base that is soluble in water
What is a neutralisation reaction
Reaction between a base and acid
Explain Mash, Basho, cashoco
Mash
Metal + acid -> salt + hydrogen
Basho
Base + acid -> salt + hydrogen + oxygen
Cashoco
Carbonate + acid -> salt + H2O + CO2
What is metallic bonding
Lattice of metal ions + sea of delocalised electrons
Describe and explain the trend in reactivity with water as you move down group 2
Forms hydroxides (+ H2) with water, outer electrons further from nucleus so are lost more easily
Explain the trend in pH and solubility reacting with water as you go down group 2 oxides
Forms group 2 hydroxides, which are strongly alkaline
As you go down, they get more alkaline because they also get more soluble
Describe the trend in group 2 carbonate solubility
As you go down the group, the solubility descreases
Compare and contrast the appearances of atomic emission spectra and atomic absorption spectra
Emission:
Dark background, colour lines
Absorption:
Black lines, coloured background
Both have more lines, which are closer together, at higher frequencies
Explain what causes the lines in an atomic emission spectra, and why they are vary for different elements
- electrons are excited up to higher energy levels
- they drop back down very quickly, releasing energy in the form of a photon of light
- the frequency of the photon is proportional to the distance dropped
ΔΕ=hf - each photon corresponds to a line on the spectra - higher energy levels are closer together so higher frequencies have lines closer together
- each element has a unique pattern of distances between energy levels, so frequency of photons emitted and therefore spectra will also be unique
State mass + mol equation
moles = mass/Mr
State vol mol equation
Moles = vol (in cm3)/1000 x concentration
State dilution equation
C1V1 = C2V2
State gas volume and mol equation
Moles = volume/24 dm3
Define periodicity and give an example
The repeating pattern of properties when elements are put in atomic number order (across a period)
Melting point (and bp) increases across a period until simple covalent nonmetals, where it drops down very low and starts to decrease
Explain physical properties of ionic substances
High mp and bp - lots of energy needed to break strong ionic bonds
Don’t conduct electricity as solid, but do in solution/molten - as ions are free to move and carry charge
Soluble - polar substance, forms ion-dipole bonds with water
Explain physical properties of simple covalent structure
Relatively low mp and bp - weak id-id bonds between molecules so little energy needed to break
Do not conduct electricity - no charged particles free to move
Not very soluble (usually) - as often nonpolar
Explain properties of giant covalent lattices
Very high mp and bp - many strong covalent bonds, lots of energy needed to break
Do not conduct electricity usually (excluding graphite, which can conduct due to delocalised electrons between carbon sheets)
Not soluble (nonpolar)
Explain properties of metals
High mp and bp - strong electrostatic attraction (metallic bonding) , lots of energy needed to break
Good conductor, delocalised electrons that are free to move can carry charge
Not soluble (nonpolar)
Name two elements that break the pattern with numbers of bonded electrons in outer shell
awkward Buggers
Beryllium and Boron
Name three groups of ionic compounds that are always soluble
All group one salts
All ammonium salts
All nitrate salts
What are the only ionic compounds that contain halogens that are insoluble
Lead (II) halide and silver halide
What are the only 4 sulfate compounds that are insoluble
Barium sulfate
Lead (II) sulfate
Silver sulfate
Calcium sulfate
What are the only two types of carbonates that are soluble
Group one carbonates
Ammonium carbonates
What does flash the cash mean
FlaSH - for positive ions
Flame test first, then add sodium hydroxide to test for precipitates
CaSH - for negative ions
Test for Carbonate first (nitric acid or HCl)
Then Sulfate (add barium nitrate)
Then Halides (precipitate with silver nitrate)
How would you prepare an insoluble salt e.g. barium sulfate, giving examples of reactants
Mix sulfate ions (sodium sulfate solution) and barium ions (barium chloride solution)
Filter to collect precipitate that forms, rinse and dry
How would you make a soluble salt using a neutralisation reaction
E.g. copper sulfate
Use acid that contains anion (sulfuric acid)
And insoluble base that contains cation (copper carbonate)
Mix and allow neutralisation to form copper sulfate solution
Filter to remove excess copper carbonate
Evaporate water by warming until crystals form
Collect crystals when mostly dry by filtration, rinse and then dry
State equation to calculate percentage uncertainty
Total uncertainty / measurement size x 100
