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.
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.