atomic structure

• relative atomic mass

  
• atomic number - the number of protons in an atom
• mass number - the total number of protons + neutrons in an atom
• mendeleev left spaces for elements that had not been discovered
• jj thompson created the plum pudding model
• rutherford's model shows that some particles deflect backwards
• bohr's model of the atom: electrons orbit the nucleus in shells
• atomic particle

  
• isotopes have the same amount of protons but a different number of neutrons
• electronic structure

  
• group 7 elements are called halogens
• group 0 elements are called noble gases
• elements with similar properties occur in vertical groups on the periodic table
• metals are found on the left side of the periodic table
• the reactivity of an element increases down group 1, as there is more space between nucleus and outer shell so it's easier to lose electrons
• non-metals are found on the right side of the periodic table
• alkali metals have low melting points because they have weak intermolecular forces due to their small size and high charge density
• noble gases don't react easily because they already have full outer shells
• boiling points will increase going down group 8 due to increase in number of electrons
• metals are malleable but are strong due to metallic bonding
• halogen atoms can gain one electron to form negative ion with full outer shell
• as you go down group 7 they are less reactive as it is harder to remove the outer electron
• more reactive halogens will displace less reactive ones
• group 1 elements all have one valence electron which makes them highly reactive
• alkali metals react with water = hydrogen gas
• alkali metal + oxygen = oxide
• alkali metal + chlorine = salt + hydrogen
• metals are good conductors of heat and electricity because they have free electrons that can move around
• non-metals do not conduct heat or electricity as their atoms are held together by covalent bonds so the electrons cannot move freely
• the noble gases are unreactive due to having full outer shells, this means there is no need to gain/lose electrons to form compounds