C1 Atomic structure & periodic table

• Isotopes are different forms of the same element with the same number of protons but different number of neutrons
• Atoms have the same number of protons and electrons, but different numbers of neutrons.
• A compound is a substance formed from two or more different elements in fixed proportions, held together by chemical bonds
• A mixture consists of two or more elements or compounds that are combined, but not chemically bonded together
• CHROMATOGRAPHY:

  put a dot of the dye mixture on the pencil line and place the filter paper in solvent. The solvent should be below the pencil line. Each different dye in the mixture will move up the paper at different rate, separating out the dyes. You’ll end up with three separate spots on your chromatography (that’s if there solvent)
• Filtration can be used (to separate)when you have a mixture of an insoluable solid and a liquid
• Crystallisation is used to separate a soluble solid from a solution
• Filtration works by passing the mixture through a filter. The liquid passes straight through, but the insoluble solid particles are caught by the filter
• to carry out crystallisation you’d need an evaporating dish and a heat source. and once you’ve got your crystals they’ll need to be filtered out of the solution, so you’d need a beaker or flask, funnel and some filter paper
• BOHR suggests that electrons orbit the nucleus in shells that are fixed distance from the nucleus. His theory stated that the electrons can only be found in these shells (and not between them)
• JAMES CHADWICK provided evidence for the existence of neutrons within the nuclei of atoms
• The plumb pudding model describes atoms as balls of positive charge with electrons stuck in them
• 1. DALTON "BILLIARD BALL"

  MODEL, 1803

  2. THOMSON "PLUM PUDDING"

  MODEL, 1897

  3. RUTHERFORD MODEL

  1909 - 1911

  4. BOHR MODEL

  1913

  5. CURRENT NUCLEAR

  MODEL, 1932

  
• Elements in the same group have the same number of electrons in their outer shell.
• Group one (alkali metals)

  Group two (alkaline-earth metals)

  Group seven (halogens)
• Metals are elements which can form positive ions which are found towards the left and bottom of the periodic table
• the reactivity of the group 1 metals increase down the group this is because the outer electron shell is further from the nucleus so is less attracted and is more easily lost
• Covalent bonds are shared pairs of electrons
• Ionic bonding is transfer of electrons
• An atom is the smallest part of an element that can exist
• daltons model is where atoms as solid spheres that could not be divided into smaller parts
• The plum pudding model is sphere of positive charge with electrons embedded in it
• scientists discovered that some alpha particles were deflected by the gold foil this showed that an atoms mass and positive charge must be concentrated in one small space (the nucleus) in the alpha scattering experiment
• The nuclear model of the atom is a dense nucleus with electrons orbiting it.
• Niels Bohr discovered that electrons orbit in fixed energy levels (shells)
• James Chadwick discovered the uncharged particle called the neutron
• Protons and neutrons are found in the nucleus of an atom.
• The relative mass of each sub-atomic particle is proton:1, neutron: 1, electron: 0 (very small)
• Relative charge of each sub-atomic particle is proton: +1, neutron: 0, electro: -1
• The atomic number on the periodic table is the number of protons in an atom
• To calculate the number of neutrons in an atom you need to do: mass number - atomic number
• Atoms have no overall charge as there are equal numbers of positive protons and negative electrons
• An element is a substance made of one type of atom
• A compound is a substance made of more than one type of atom chemically bonded together.
• a mixture is two or more substances that are not chemically bonded together.
• An isotope is atoms of the same element with the same number of protons but a different number of neutrons
• The 4 physical processes that can be used to separate mixtures are: filtration, crystallisation, fractional distillation and chromatography
• The relative mass is the average mass of all the atoms of an element
• The modern period table is ordered by atomic number
• The early lists of elements are ordered by atomic mass