Atomic Structure And Periodic Table Flashcards
Atoms
Make up all substances and are the smallest part of an element
Compounds
Contain 2 or more elements chemically combined together
Mixture
Two or more elements or compounds not chemically combined
Mixture separation techniques
- filtration
- chromatography
- crystallisation
- simple distillation
- fractional distillation
Plum pudding model
Atom is a ball of positive charge with negative electrons embedded in it
Alpha particle scattering experiment
- alpha particles fired at a thin sheet of gold foil
- most particles passed through
- some particles were deflected
Results of alpha particle experiment
- mass was concentrated in the middle as a nucleus
- the nucleus was positively charged
- atom was mostly empty space
Neil Bohr
Suggested electrons orbit the nucleus at specific distances
James Chadwick
Discovered neutrons
Rutherford’s nuclear model
- small positively charged nucleus surrounded by negatively charged electrons
- mostly empty space
Order in which the subatomic particles were discovered (first to last)
- electrons
- nucleus
- protons
- neutrons
Mass of subatomic particles
Proton = 1
Neutron = 1
Electrons = very small
Isotope
Atoms of the same element with different number of neutrons
Early periodic table
Ordered in atomic weight
Mendeleev
Ordered his table in order of atomic mass BUT left gaps for undiscovered elements
- He switched some elements to fit chemical properties
Modern periodic table
Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct
Group 1 - Alkali metals
- one electron in their outer shell
- reactivity increases down the group
- react with water to create metal hydroxide and hydrogen
Reaction of group 1 with water
Lithium -> fizzes steadily + gradually disappears
Sodium -> fizzes rapidly + melts
Potassium -> ignites with lilac flame
Gas produced is hydrogen
Reaction of group 1 with chlorine
Lithium -> white powder produced
Sodium -> burns with bright yellow flame
Potassium -> more vigorous reaction than sodium
Group 0 -> Noble gases
- full stable outer shell
- unreactive
- boiling points increase going down
Transition metals
- strong
- high melting points and densities
- have ions with many different charges
- form coloured compounds
- good catalysts
Explain why the reactivity increases as you go down group 1
- easier to lose electrons
- as there is a greater distance between outermost electron and nucleus
- so less attraction between them
- increased shielding from increased shells
Explain why the reactivity decreases as you go down group 7
- harder to gain electrons
- greater distance between outermost electron and nucleus
- due to more energy shells/levels
- less attraction between (+) nucleus and (-) that is trying to be gained
- increased shielding
Group 7 - Halogens
Fluorine - yellow-green gas
Chlorine - yellow-green gas
Bromine - red-brown liquid
Iodine - grey solid + purple vapour (brown in solution)
Reactivity decreases as you go down
