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Revision C1 (Periodic table (Mendeleev left gaps in the Periodic Table…
Revision C1
Periodic table
Mendeleev left gaps in the Periodic Table because he thought that new elements would be discovered, each elemnet had an atomic number of 1 and higher.
Dobereiner put elements in order based on chemical propertied and atomic mass, formed groups of three middle element of triad had an atomic mass the average of the other two.
Modern Periodic Table is laid out in order of atomic number . It consists of groups that go downwards and periods which go across. The metals are to the left, non-metals are to the right and metalloids dividing them
Newlands said that every 8th element has similar properties, listed elements in rows of 7 known as octaves, pattern broke down at the transition metals
Sepertating Mixtures
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Crystallisation is where you need to obtain a sample of pure salt. From that solution following filtration. You need to separate them by evaporation
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Simple Distillation is where a solution is heated and boiled to evaporate the solvent. The vapour given off then enters a condenser. This us a outer glass tube with water flowing through it that acts as a cooling jacket. it goes from a liquid to a gas to a liquid again
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Plum Pudding Model
Plum Pudding model is where JJ Thomson suggested that the atom consists of positive dough and then negative electrons would be stuck in it. This was consistent with the evidence known at that time.
Thomson
Thomson thought that the electron just float around, however, Rutherford belived that the electrons orbit the nueclus just like planets orbit the sun.
Atomic Structure
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In each Group in the periodic table, the elements depend on how many electrons that element has in their outer shell. Every Element in Group 7 all of them have 7 electrons in their outer shell
Group 1
Lithium, Sodium, Potassium, Rubidium, Caesium
An atom is held together by the force of attraction between protons which are positive and electrons which are negative. When group one metals react they want to get rid of their outer electron.This occurs more easily the lower down group one you go as the atom is getting bigger and the electron has less attraction to the proton so can be lost easier
Group 7
Group 7 is an atom is held together by the force of attraction between protons which are positive and electrons which are negative. When group 7 halogens react they want to gain an electron so they have a full outer shell. This occurs less easily the lower down group 7 you go as the atom is getting bigger. This means the electron has less attraction to the nucleus so is harder to gain
Fluorine,Chlorine,Bromine,Iodine
Group 0
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Helium, Neon,Argon, Krypton,Xenon,Radon
Isotopes is where you have different forms of the same element which have the same number of protons and electrons but a different number of neutrons
Noble Gases are stable and unreactive because they have an complete outer shell they don't need to lose or gain any electron
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