C1 Flashcards
Atoms
Smallest part of an element that can exist.
Made up of protons neutrons and electrons.
The table shows relative mass and electric charge of these particles.
Mass is given relative to the mass of a proton.
Protons and neutrons have same mass, electrons are far lighter.
Structure of an atom
Atoms radius is about 0.1nm.
Central nucleus contains protons and neutrons.
Nucleus is surrounded by electrons which move around it in energy levels/shells.
Atomic number
The no. of protons that an atom contains = its atomic number.
Atoms of different elements have different numbers of protons.
It is the no. of protons that determines which element it is.
E.g. all atoms with 6 protons are carbon atoms.
Mass number
All atoms are neutral bc the no. of positive protons is the same as the no. of negative electrons.
Most of the mass of an atom is due to the protons and neutrons. They have the same mass as each other.
The mass no. = the sum of protons and neutrons in an atom.
Isotopes
Most elements have atoms with different numbers of neutrons.
Isotopes are atoms with the same number of protons but a different number of neutrons.
So isotopes have the same atomic number but a different mass number.
Relative atomic mass
The average mass of atoms of that element taking into account the mass and amount of each isotope it contains.
Ar=total mass of all atoms of element/total number of atoms of that element.
Electron arrangement
Electrons in an atom are in energy levels or ‘shells’. They occupy the lowest available energy levels.
Lowest energy level is the one closest to the nucleus and can hold up to 2 electrons. Up to 8 occupy the second energy level with the next 8 occupying the third energy level. The next 2 electrons occupy the fourth.
Element
A substance containing only one type of atom.
Compound
A substance containing elements and/or compounds that aren’t joined together.
State symbols
Gas (g)
Liquid (l)
Solid (s)
Aqueous (aq) - dissolved in water
Atom timeline - 1
(460-370BC) demokrites, a Greek philosopher, found out that all matter could be divided and subdivided until there would be a tiny particle that couldn’t be divided any further.
Atom, come from atomos, Ancient Greek for indivisible.
Atom timeline - 2
Plum pudding model created by JJ Thompson in the late 19th century.
The atom was thought to be a speed of positive charge with negatively charged electrons dotted around inside it like plums in a pudding.
Proved incorrect in 1905.
Atom timeline - 3
Rutherford designed an experiment to test the plum pudding model, carried out by Geiger and Marsden in early 20th century. A beam of alpha particles aimed at very thing gold foil, their passage through detected. Some particles emerged at different angles, some came straight back. Positively charged particles were being repelled and deflected so there must be something positive in the centre.
Atom timeline - 4
Neil’s Bohr proposed that electrons are orbiting, in 1915. Has an atom consisting of a small positively charged nucleus orbited by negatively charged electrons. Radiation is emitted when an electron moves from one orbit to another. Not just one electron, a few, depending on the element.
Atom timeline - 5
Discovery of proton. Rutherford revisited Bohr’s idea of negatively charged electrons and saw there must be something positive, the proton. We must have more than one to balance the negatively charged things.
Atom timeline - 6
Discovered in 1932, James Chadwick used scattering data to calculate the mass of the neutron particle. The middle/ neutron has no charge.
Chromatography
- Put the test substance in a spot at the bottom of the paper.
- The solvent moves up the paper.
- Takes the soluble particles with it.
Spots relate to stationary phase.
The retention factor is a way of comparing how far different compounds have travelled, distance spots travel, and different solvents travel.
Distillation
The mixture is heated. The liquid with the lowest boiling point will turn into a gas.
Shows which substances in a mixture have the highest/lowest boiling point.
Filtration
Pour the mixture into the filter funnel. The water (filtrate) will pass through the filter paper but the insoluble solid (residue) won’t.
Solute
Substance that dissolves in a liquid to form a solution.
Solvent
The liquid in which a solute dissolves.
Insoluble
Describes a substance that won’t dissolve.
Soluble
Describes a substance that will dissolve.
Solution
The mixture formed when a solute has dissolved in a solvent.
Saturated solution
A solution in which no more solute can be dissolved in the solvent.
No. Of atoms
Mass number - atomic number
Or
Top - bottom
Isotopes 2
Isotopes of an element have a different number of protons and neutrons.
As they have the same number of electrons they react chemically in the same way.
Isotopes of an element have a different number of neutrons hence the mass no. is different.
Electronic structure - diagram
Circles are the electron shells.
Each x represents how many protons also the no. of electrons there are in the element.
Group no. is the number of electrons on the outer shell.
2, 8, 8.
Group 0
Noble gases.
Main elements: helium, neon, argon, krypton, xenon and radon.
All have stable electron structures.
Colourless. Low boiling points. Boiling point increases as the atoms get heavier going down the table.
Very unreactive.
Group 7
The halogens
Main elements: fluorine chlorine bromine, iodine.
Have similar chemical and physical properties as they all have 7 electrons in outer shell.
Very reactive as they only need to gain 1 electron in order to have a stable structure like the noble gases.
Diatomic molecules: F2, Cl2..
Properties of group 7
Each is very toxic.
Low melting and boiling points - both increase as you go down the group.
They react with non metals by sharing electrons to form compounds made of molecules.
All react easily with metals by the transfer of electrons from the metal to the halogen forming ionic compounds. Halogens make 1- ions.
Group 1
Metal + water - metal hydroxide + hydrogen.
E.g. 2Li + 2H2O - 2LiOH + H2
Mass gets bigger as you go down.
No. Of electron shells increases.
Energy needed to remove electron lessens.
Known as alkali metals bc they form alkali solution with water.
Why does group 1’s reactivity increase as you go down?
Outer electrons are further away from the nucleus (larger atom).
Nucleus contains protons that attract the electrons (nuclear charge).
Further away from the nucleus, less attraction is felt by the electron (shielding) and less energy is needed to remove it from the atom.
Lithium
Red flame Silvery grey colour Not hard Tarnishes very quickly Floats When reacting with water: effervescent, steam, sound
Sodium
Orange flame Silver colour Softer than lithium Quicker to tarnish Floats When reacting with water: moves around, melts
Potassium
Lilac flame Silver colour Softer Quick to tarnish Floats When reacting with water: sets alight, sound.
Rubidium
Red/orange flame Silver colour Softer Tarnishes quick Floats When reacting with water: blows up
Caesium
Red/orange flame Silver Softest Tarnishes quickest Floats When reacting with water: blows up, destroying the container too.
