a simple model of the atom, relatommass, isotopes etc

• Atoms are the smallest part of an element that can exist
• Chemical reactions always involve the formation of 1 or more new substances and often involve an energy change.
• compounds: a substance made up of two or more elements chemically combined in fixed proportions.
• Compounds can only be separated into elements by chemical reactions
• Mixture: A substance made up of two or more elements or compounds that are not chemically combined
• mixtures can be separated using physical methods such as filtration, distillation, evaporation and chromatography. (no new substances are made)
• atom size: radius of about 0.1nm
• mass number: the total number of protons and neutrons in an atom of an element
• isotopes: atoms of the same element with different numbers of neutrons
• atomic number: the number of protons in an atom of an element.
• isotope equation: $(isotope 1 mass* abundance)+$$(isotope 2 mass* abundance))/100$