C1 Atomic Structure Flashcards
Element
A substance made up of only 1 type of atom
Significance of symbols used in equations
They show us what atoms are involved and how they are bonded together
Why mass is conserved in a chemical reaction
No new atoms have entered or left the system
Law of conservation of mass
Mass cannot be created or destroyed in a chemical reaction
Difference between plum-pudding and nuclear model of atom
Plum-pudding model - positive sphere with negative randomly placed in sphere
Nuclear - Central positive tiny nucleus with negative charges
Why model of atom changed overtime
Technology advanced
How evidence from scattering experiments changed the model of the atom
Alpha scattering led to plum-pudding model replaced with nuclear model
Relative charges and masses of subatomic particles
Relative charge
Protons = +1 Neutrons = 0 Electrons = -1
Relative mass
Protons and neutrons = 1
Electrons = 0.0005
Number of protons = atomic number
Number of electrons = atomic number
Number of neutrons = ?
Mass number - atomic number
Ion
Charged particles that have either lost or gained electrons
Isotope
Forms of element that have same number of protons but different numbers of neutrons
How to describe isotopes using atomic model
Atoms with same number of protons but different numbers of neutrons
Why ions have a charge
Because number of electrons does not equal number of protons
Relative size of atom and its nucleus
-10
Atom - diameter 10 m
-15 Nucleus - diameter 10 m
Why chlorine doesn’t have a full mass number
Because of isotopes
The maximum number of electrons in the first 3 energy levels
First energy level - 2
Second energy level - 8
Third energy level - 18
Mixture
A compound made up of 2 or more elements not chemically bonded
Radius of an atom
0.1 nanometres
-14 1 x 10 m
Why is the nucleus a positive charge
Because it has protons
Mass of electrons
Electrons have no mass
Atomic number
Mass number
23 -
Na
11 -
Page 12
Atomic number
Tells you how many protons there are
Mass number
Tells you total number of protons and neutrons in the atom
How to get number of neutrons
Mass number - Atomic number
Do elements consist of atoms with the same atomic number
True
What do number of protons in an element decide
What type of atom it is
The difference between isotopes
Same atomic number but different mass numbers
Example of a pair of isotopes
Carbon-12 - 6 neutrons
Carbon-13 - 7 neutrons
Abundances
Amounts
Relative atomic mass =
Sum of (isotopic abundance x isotopic mass number)
________________________________________________________
Sum of abundances of all isotopes
Which part of an atom isn’t affected when a bond is made
The nuclei
What are compounds represented by
Formulas
What does the mixture air contain
Mainly nitrogen, oxygen, carbon dioxide, argon
Paper chromotography process
Steps 1-5
Draw line near bottom of filter paper
Add a spot of ink to line
Place sheet in beaker of solvent
Make sure ink isn’t touching the solvent
Place lid on top of container
Paper chromotography process
Steps 6-7
Solvent seeps up paper carrying ink with it
Each different dye in ink will move up at different rates
Each dye will form a spot in different place - 1 spot per dye in ink
Paper chromotography process
8-10
If any dyes in the ink are insoluble they will stay on the baseline
When solvent has nearly reached top of paper, take paper out of beaker and leave to dry
The end result is a pattern called a chromatogram
Why do you have to use pencil to draw a line near bottom of filter paper
Pencil marks are insoluble and won’t dissolve in solvent
Why shouldn’t ink touch the solvent
Don’t want ink to dissolve into it
Why do you need to place lid on top of container
To stop solvent from evaporating
Methods of separating mixtures
Filtration
Crystallisation
Chromotography
Distallation
2 ways to separate soluble solids from solutions
Evaporation
Crystallisation
Evaporation method
Pour solution in evaporating dish
Slowly heat solution
Solvent will evaporate and solution becomes more concentrated
Crystals form
Keep heating evaporating dish until all you have left are dry crystals
Crystallisation method
Steps 1-3
Pour solution into evaporating dish and gently heat solution
Some solvent will evaporate and solution will get more concentrated
Once some solvent evaporates or when you see crystals start to form (point of crystallisation) remove the dish from the heat and leave solution to cool
Crystallisation method
Stels 4-6
The salt should start to form crystals as it becomes insoluble in cold highly concentrated solution
Filter crystals out of solution and leave them in warm place to dry
Distallation
Used to separate mixtures which contain liquids
2 types - simple and fractional
What is simple distallation and fractional distallation used for
Simple distallation - used to separate out solutions
Fractional distallations - used to separate a mixture of liquids
Simple distallation process
Solution heated
Vapour is cooled, condenses (turns back into a liquid) and is collected
Rest of solution is left behind in the flask
Fractional distillation process
Steps 1-4
Put mixture in flask
Stick a fractionating column on top then heat it
Different liquids will have different boiling points so will evaporate at different temperatures
The liquid with lowest boiling point evaporates first
Fractional distillation process
Steps 4-7
When temperature of thermometer matches boiling point of this liquid it will reach top of the column
Liquids with higher boiling points mights also start to evaporate
But the column is cooler towards the top so will only get part of the way up before condensing and run back down towards flask
When the first liquid has been collected raise temperature until the next one reaches the top
How would you know what separation technique to use for a given mixture?
Dependent on the properties of the mixture components
How do the chemical properties of a mixture relate to the chemical it is made from
The chemical property of each substance in a mixture does not change
How fractional distillation can separate miscible liquids with similar boiling points
A mixture of liquids is boiled and the resulting vapors travel up a fractionating column and separate
Properties of an element
Atomic radius
Electronegativity
Ionization energy
Properties of a mixture
No fixed composition
No fixed melting points
No fixed boiling points
Properties of a compound
Pure substance
Fixed melting point
Fixed boiling point
John Dalton
1803
Described atoms as solid spheres
Said different spheres are made up of different elements
J J Thomson
1897
Plum pudding model
A ball of positive charge with electrons scattered over it
Ernest Rutherford
1909
Nuclear model
Tiny positive charged nucleus at the centre, electrons orbit the nucleus
Niels bohr
1913
Rutherford-bohr model
Positive charged nucleus with electrons surrounding it
Erwin Schrodinger
1926
Quantum model
Stated electrons don’t move in set paths around the nucleus but in waves
Electrons orbit positive nucleus in waves
Ernest Rutherford and his student Ernest Mardon’s experiment
Alpha particle scattering experiment
They fired positively charged alpha particles at a thin sheet of gold
They expected particles to pass straight through the sheet or slightly deflected
Some particles went straight through the gold sheet but some were deflected more than expected and a small number were deflected backwards
So this disproved plum pudding model
Why did Rutherford expect particles to go straight through sheet
Positive charge of atom was thought to be very spread out through the ‘pudding of an atom’
Why was the nuclear model atom mostly an empty space
A ‘cloud’ of negative electrons surrounds nucleus
Proton, electron, neutron,
Order of discovery
Electron, proton, neutron (earliest to latest)
Electron - J J Thomson 1897
Proton - Ernest Rutherford early 20th century
Neutron - James Chadwick 1932
What are the energy levels which electrons orbit called
Shells
How many electrons are allowed in each shell
2 - 1st shell
8 - 2nd shell
8 - 3rd shell
Electronic structure of Nitrogen
Nitrogen has atomic number 7 (so 7 protons)
The first shell can only take 2 electrons and the 2nd takes maximum of 8
So electronic structure of nitrogen would be 2, 5
Electronic structure of magnesium
Atomic number 12 (so has 12 protons so it has 12 electrons)
1st shell takes 2, 2nd shell takes 8, 3rd shell takes 8
2, 8, 2
Atom
Smallest part of an element
What do elements in same group have in common
Same chemical properties
Reactants
Products
Reactants - substances you start with
Products - the new substances made in chemical reaction
Hydrogen + oxygen ———-> water
Reactants?
Products?
Reactants - hydrogen + oxygen
Products - water
Aqueous solution (aq)
Substances dissolved in water
Precipitate
Solid formed in reaction between 2 solutions
How did Niels Bohr discover electrons 1914
He noticed light given out when atoms were heated had specific amounts of energy
Why does sand become residue rocksalt separation technique
Sand grains are insoluble so cannot pass through filter paper
Why does yellow dye move further up the paper chromotogram technique
The yellow dye is more soluble in water than the red dye
Molecules
Pairs of atoms
Filtration use
Separates an insoluble solid from a liquid
Crystallisation use
Separates a soluble solid from a liquid
Simple distallation use
Separates a liquid from a dissolved solid
Fractional distallation use
Separates two or more liquids which have different boiling points
Chromotography use
Separates two or more dissolved solids from a solution
Reading on thermometer during simple distallation
100°C
Diamater of indium atom in metres
-10
3.10 x 10 m
Diamater of indium atom in metres
-10
3.10 x 10 m
