Atomic Structure

• In an element all of the atoms are the same. They have the same number of protons and electrons.
• Compounds contains two or more elements chemically combined in fixed proportions.
• A mixture is a substance that contains two or more elements or compounds that are not chemically combined.
• A molecule is 2 or more atoms bonded together by covalent bonds.
• Filtration is used to separated an insoluble solid from a liquid.
• Insoluble means a solid will not dissolve in a liquid.
• State symbols shows us whether an element is a solid liquid or a gas.
• Crystallisation is used to separate a soluble sold from a liquid.
• In simple distillation you first evaporate the liquid by heating it then you condense the vapour back to a liquid by cooling it.
• Fractional distillation is the separation of a mixture of different liquids but they must have different boiling points.
• Chromatography separates substances based on their solubility in a solvent.
• A solvent is a substance that dissolves another substance in it.
• In chromatography a pure compound would be a single spot on the paper. However compounds in a mixture may separate into different spots depending on the solvent.
• In the plum pudding model, an atom is a ball of positive charge with negative electrons embedded in it.
• The alpha scattering experiment was when they fired alpha particles at gold foil and observed the scattered alpha particle.
• The radius of an atom is around 0.1 nm.
• The charge of protons is + and relative mass of 1.
• The charge of a neutron is 0 with a relative mass of 1.
• The charge of electron is - with a relative mass is very small.
• Mass number is the total number of protons and neutrons in an atom's nucleus.
• Atomic number is the number of protons in an atom of an element.
• Isotopes is an element with the same number of protons and electrons however a different number of neutrons.
• Ions are atoms which have an overall charge and this is due to the ions which have lost or gained electrons.
• Relative atomic mass = (M of iso1 x Percent A of iso1) + (M of iso2 x Percent B) / 100
• In the centre of an atom there are protons and neutrons and in the energy shells there are electrons.
• The first energy level can only hold a maximum of 2 electrons and the rest of the shells can hold 8.
• All elements in a group have the same number of electrons in the outer energy level.
• Dmitri Mendeleev developed the first modern periodic table by arranging all the elements in increasing the atomic weight.
• Mendeleev left gaps in the periodic table for undiscovered elements.
• In the modern periodic table it was ordered in atomic weight.
• Group 0 are called noble gasses which are non-reactive metals.
• Atoms are stable when they have a full outer energy level.
• All noble gasses have a full outer shell.
• In group 0 as the relative atomic mass increases the boiling point decreases as you go down the group.
• Metals are found in the left and centre of the periodic table and on the right hand side you can find the non-metals.
• In the centre of the period table you have transition metals which aren't as reactive.
• When metals react they lose electrons to achieve a full outer shell.
• Metals always form positive ions.
• All group 1 metals have 1 electron in their outer shell, so they are all very reactive.
• Group 1 metals are soft.