- Created by: maddieecarr
- Created on: 07-12-19 10:09
- all substances are made up of atoms
- the periodic table lists all the chemical elements with 8 main groups containing elements with similar chemical properties.
- elements only contain one type of atom
- compounds contain more than one type of atom.
- an atom has a tiny nucleus at its centre, surrounded by electrons.
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C1.2: Chemical equations
- no new atoms are ever created or destroyed in a chemical reaction.
- total mass of reactants = total mass of products
- there is the same number of each type of atom on each side of a balanced symbol equation
- you can include state symbols to include extra information in balanced symbol equations:
- (s) = solid
- (l) = liquid
- (g) = gas
- (aq) = aqueous solution
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C1.3: Separating mixtures
- a mixture is made up of two or more substanced that are not chemically combined together.
- mixtures can be separated by physical means:
- simple distillation
- fractional distillation
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C1.4: Fractional Distillation and Paper Chromatogr
- fractional distillation is an effective way of separating miscible liquids using a fractionating column.
- the separation is possible as the liquids in the mixture have different boiling points.
- paper chromatography separates mixtures of substances dissolved in a solvent as they move up a piece of chromatography paper.
- the different substances are separated because of their different solubilities in the solvent used.
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C1.5: History of the Atom
- ideas about atoms have changed over time
- new evidence has been gathered from the experiments of scientists who have used their model of the atom to explain their observations, calculations and discoveries.
- key ideas have been proposed successfully by:
- Dalton - little, hard spheres; cannot be divided or split; building blocks of nature
- Thompson - discovery of the electron; 2000x smaller than lightest atom
- Rutherford - positive charge concentrated; electrons must orbit; protons are positive
- Bohr - electrons must orbit nucleus at set distances; high to low energy level
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C1.6: Structure of the Atom
- atoms are made of protons, neutrons and electrons
- protons = +1 charge; relative mass = 1
- neutrons = 0 (neutral) charge; relative mass = 1
- electrons = -1 charge; relative mass = 1/2000
- atoms contain equal numbers of protons and electrons, producing a neutral charge overall.
- atomic number = number of protons
- mass number = number of protons and neutrons
- atoms of the same element hae the same number of protons and electrons in their atoms.
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C1.7: Ions, Atoms and Isotopes
- atoms that gain electrons form negative ions. if they lose electrons they form positive ions.
- isotopes are atoms of the same element with different numbers of neutrons.
- an isotope's chemical properties are identical but it may have different physical properties, such as density.
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C1.8: Electronic Structures
- the electrons in an atom are arranged in energy shells
- the lowest energy level - the first shell - can hold up to 2 electrons, the next can hold up to 8 electrons.
- the next shell only begins to fill when the one below is full.
- the number of electrons in the outermost shell of an element's atoms determines the way in which that element reacts.
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