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C1 - ATOMIC STRUCTURE, DISTILLATION, he suggested, 4) RUTHERFORD, IONS,…
C1 - ATOMIC STRUCTURE
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1.7 - IONS, ATOMS, ISOTOPES
- when an atom gains one or more electrons it gets an overall negative charge because there are more electrons than protons. you can say the atom has become a NEGATIVE ION
- if an atom looses one or more electron it becomes overall positive, you can call it a POSITIVE ION
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- if n oxygen atom gains 2 electrons its protons stay 8 but its electrons change, so from being -8 they become -2 as they gained 2 electrons. So the overall charge on the oxygen atom is negative so it becomes O^2- as its overall charge formed is 2-
- atoms of the same element with different neutrons are called ISOTOPES
- sometimes an extra nucleus to the atom can make it radioactive
1.1 - ATOMS
- all substances are made of tiny particles called atoms
- They can combine forming substances called elements
- An atom is the smallest part of an element that cal exist
- elements can share some properties with other elements whereas some are completely different
- chemical symbols are abbreviations of the element in a way that all nations can understand (e.g - Na (sulfur))
- The symbols are found in the periodic table
- in the periodic table groups vertically down whereas periods are horizontal.
- atoms bonded together are called compounds.
- all atoms are made up of a tiny central nucleus
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1.2 - CHEMICAL EQUASIONS
- chemical equations show the reactants and the products
- e.g of a word equation = hydrogen + oxygen -> water
- balanced equation = there is the same number of each
type of atom on each side (CaCO3 → CaO + CO2
- atoms CANNOT be created or destroyed in reactions
- total mass of reactants = total mass of products = LAW OF CONSERVATION
- state symbols : (s) meaning solid. (l) meaning liquid.
(g) meaning gas, and (aq) meaning substance dissolved in water.
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1.5 - HISTORY OF ATOMS
1) JOHN DALTON
- Atoms were tiny hard sphere
- each chemical element had its own atom that differed from others from their mass
- he believed that atoms could not split and divide them self and they were the building blocks of nature
2) JJ THOMSON
- he discovered the electron by applying high voltages to gases at low pressures
- the electrons were attracted to positive charges showing they must be negatively charged
- Dalton's idea they there wouldn't be split or divided was changed
- he suggested a different model showing electrons in a sphere of positive charge. He called this a plum pudding showing the electrons where the plum pieces in the pudding
3) GEIGER AND MARSDEN
- they fired dense, positive charged particles (alpha particles) through a thin gold foil which changes the plum pudding model
- Rutherford suggested that Thomson's model wasn't possible, the positive charge must be concentrated in a small spot in the middle of the atom. Otherwise the large positive particles fired at the foil could never be repelled back towards their source.
- it was proposed that the electrons must be orbiting around the nucleus (the center of the atom) which contains very dense positively charged PROTONS
5) NIELS BHOR
- he notices that the light given out when the atoms were heated specific amounts of energy
- he suggested that the electrons must be orbiting the atoms at set distances in fixed ENERGY LEVELS or SHELLS
6) JAMES CHADWICK
- scientists at the time believed there were 2 sub-atomic particles in the nucleus, one was the protons but they couldn't figure out the second.
- Because neutrons have no charge, it was very difficult to do experiments. This was until Chadwick did an experiment that could only be explained by the existence of neutrons
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