Atomic Structure

• element is a substance made from one type of atom
• compound is a substance made up of two or more different types of atoms joined together by chemical bonds.
• the total mass of the product formed in a reaction is equal to the total mass of the reactants
• the subatomic particles are protons , neutrons and electrons
• same number of protons and electrons
• electrons orbit the nucleus on energy shells at fixed distances
• relative atomic mass = protons and neutrons
• atomic number = number of protons
• neutrons = relative atomic mass-atomic number
• protons have a relative charge of +1 (positive)
• neutrons have a relative charge of 0 (neutral)
• electrons have a relative charge of -1 (negative)
• proton has a mass of 1
• neutrons have a mass of 1
• electrons are very small (1/2000)
• atoms are neutral because the number of protons and electrons are the same so they cancel each other out and neutrons have no charge so it makes no difference.
• 1st shell= 2 electrons 2nd shell= 8 electrons 3rd shell= 8 electrons 4th shell= 18 electrons
• group number tells u the number of electrons on the outer shell of an atom
• noble gases (group 0) are non-metals and have full outer shells
• radius of an atom is approximately 0.1nm
• an ion is an atom that has gained or lost and electron
• loosing an electron makes the ion positive
• isotopes are atoms of the same element with a different amount of neutrons in the nucleus
• gaining an electron makes an ion negative
• different isotopes have different chemical properties e.g different densities or radioactive
• plum pudding model- sphere of positive charge embedded with negatively charged electrons,no empty spaces,mass evenly distributed by J.J Thomson
• • Nuclear model- densely packed positively charged nucleus, negatively charged electrons orbit the nucleus,most of the mass is concentrated at the nucleus,majority empty space by Rutherford
• Gold foil experiment - Positively charged alpha particles were fired at a thin sheet of gold foil.Majority of the alpha particles passed through but 1 in 10000 were deflected.This proved that the atom had a dense positive nucleus that was tiny in the centre of the atom.
• electrons were discovered first , then protons and then neutrons.
• a mixture is a substance that contains two or more elements or compounds that are not chemically combined
• filtration-separate an insoluble solid from a liquid.The residue is left in the filter paper and the liquid that travels through is known as the filtrate
• crystallisation/evaporation-separates the soluble solid from a liquid ,the liquid evaporates leaving the solid behind
• distillation-separates a soluble solid from a liquid but the liquid is retrieved.The condenser cools down the liquid.