C1 atomic structure and the periodic table Flashcards
Element
A substance that cannot be broken down chemically
Compound
A substance that contains at least two different elements chemically combined and fixed proportions
Elements
Are made up of atoms that are all the same
Compounds
Are made from atoms or charged atoms of different elements which are been chemically joined together
Mixtures
Can be easily separated because of the chemicals in them or not join together.
Mixture of separation techniques
Filtration, crystallisation, simple distillation, fractional distillation and chromatography.
Democritus
400 BC
Describe the materials has been made of small particles which could not be divided. These particles were atoms. He had no evidence
John Dalton
1803
He described an atom a billiard ball which could not be divided
J.J. Thomson
1897
Who describes atoms using a plum pudding model. The negative electrons were thought to be embedded in a ball of positive charge (protons)
Geiger and Marsden
1909
They conducted an experiment with gold leaf and alpha particles. This showed that the atom had a positively charged nucleus in the centre where most of the mass of the atom is concentrated and much of the atom was empty space
Niels Bohr
1913
He confirmed previous experiments although explained that electrons orbiting the nucleus
James Chadwick
1920
Term proton was used for positively charged atoms
1932
Neutron discovered
Atoms
Is made up of a nucleus that is surrounded by electrons
Electron shells
Electrons occupy the space around the nucleus in shells. The space between the nucleus and the electron shells is empty space.
Atomic radii
A typical atomic radius is about 0.1 nm (1×10 to the -10 m)
However the radius of an atom increases within a group of elements. The atomic radii a Li,Na,K increase as more electrons are added to the atom
The atomic number
The number of protons/ electrons in an atom
Relative atomic mass
Number of protons and neutrons
Isotopes
A form of an element that has the same number protons but different number of neutrons