Chemistry

• Matter is anything that takes up space and has mass
• All matter is made up of atoms
• An element is the name we give to different types of atoms
• Compound is made up of 2 or more different types of atoms chemically bonded together
• Molecule is a group of 2 or more atoms that are chemically bonded together
• The atomic number is equal to the number of protons
• Subatomic particles include: electrons, protons and neutrons
• The atomic mass is equal to the number of protons + the number of neutrons
• The mass number goes on top while the atomic number (protons) go on the bottom
• Isotopes are a different version of an element due to different number of neutrons therefore different number of mass
• Cations are positive ions
• Ions are charged because they have lost/gained electrons
• Cations are positively charged because they have lost electrons
• Unstable isotopes decay and this changes their structure and releases energy in the form of radiation
• Anions are negative ions
• Anions are negatively charged because they have gained electrons
• An ionic bond occurs when two oppositely charged ions attract each other
• Alpha particle is identical to the nucleus of a helium atom
• Alpha particles can be stopped by skin or a sheet of paper
• Carbon-14 is used for radiocarbon dating
• Beta particle can be stopped by your skin or a layer of clothing or a sheet of aluminium
• Gamma can be stopped by a thick layer

  of concrete or lead
• The atomic number determines how many protons an element has
• Beta particles are produced when a neutron decays into a proton and an electron
• After Beta decay the new atom gets 1 more proton than the original, but the mass stays the same
• Radioactive decay occurs when unstable atoms spontaneously change into more stable ones, releasing energy as they do so.
• An ion is an atom that has gained or lost electrons so there is no longer an equal number of protons and electrons.
• A positive ion (cation) is formed when a metal atom loses electrons whereas a negative ion (anion) is formed when a non-metal atom gains electrons
• Polyatomic ions are an ion that is made up of two or more atoms
• Ionic compounds are formed when a cation combines with an anion
• Salt can be used to identify to ionic compounds
• Radio isotope is an unstable form of a chemical element that releases radiation as it breaks down and becomes more stable
• Radioactive half-life is the time required for a quantity of a radioisotope to decay by half.
• Chemical reactions release or absorb energy due to the difference in the energy stored in the chemical bonds of the reactants and products
• An endothermic reaction is a reaction where heat is absorbed from its surroundings
• A exothermic reaction is a reaction where heat is released into its surroundings
• Some common exothermic reactions include ; cellular respiration, combustion and freezing
• Some common endothermic reactions include; photosynthesis, water evaporation and ice melting
• The law of conservation of mass states that matter cannot be created nor destroyed during a chemical reaction
• The main properties of an acid include: sour taste, turns blue litmus paper red, pH below 7