Key Chemistry Concept: Chemical reactions occur by atoms transferring or sharing electrons with each other. However, ONLY the electrons that occupy the outermost shell of atoms are involved in electron transfer or electron sharing between atoms.The electrons that orbit closer to the nucleus are, by definition, not in the outermost shell, and are therefore (usually) unaffected during chemical reactions. Valence number The
Read moreWhat are the relationships between atom, element, molecule, ion, compound and mixture? Matter is made up of repeating units of atoms, molecules or ions. An element is a substance that contains only one type of atom as its repeating unit. A monatomic element has a single atom (e.g. copper, sodium or helium) repeating unit. Whereas, a polyatomic element, has a multiple atom
Read moreElectrons occupy particular energy levels Each electron in an atom is at a particular energy level (in a particular shell). 1st shell (the ‘innermost’) shell can occupy a maximum of 2 electrons 2nd shell (‘outside the first shell’) can occupy a maximum of 8 electrons 3rd shell (‘outside the second shell’) can occupy a maximum of 8 electrons At GCSE level, because
Read moreWhat makes a chemical reaction occur? Reactants ‘react’ together to make Products. A + B → C + D (A and B are reactants) (C and D are products) When different substances (elements or compounds) react together, reactant atoms ‘break’ their chemical bonds and make new
Read morePeriodic Table This is a table-like chart that shows all the elements with their corresponding symbols- there are just over 100 different elements! The horizontal rows in the periodic table are called periods and the vertical columns are called groups. The Periodic Table has 8 Groups: starting from the left is Group 1, then Group 2… Group 8 is also
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