sem 1

• Vertical columns

  groups
• Horizontal rows

  periods
• electrons

  negative
• neutrons

  neutral
• atomic number

  number of protons in an atom
• mass number

  total number of protons + neutrons in an atom
• group 1

  Alkali metals (react strongly w water to form a basic solution)
• group 2

  Alkaline earth metals
• group 17

  halogen group (brightly coloured elements)
• group 18 


  noble gases (inert and don't readily react with other substances)
• valence electron 


  electrons in the outermost shell
• what does the number of valence electrons determine?

  the properties of elements because they are involved in chemical reactions
• stable / chemically inert

  elements with full outer shells which aren't very reactive
• atoms in the same group of the periodic table have: 


  the same number of valence electrons in their outer shells.

  Eg. lithium period 2 so has 2 shells
• electrons in same shell ... 


  are at same energy level
• shells closer to the nucleus...

  are at lower levels of energy
• electrons further from the nucleus 


  require less energy to remove them from the atom
• electrons closer to the nucleus

  greater attraction (nucleus is + charged)
• most metals give off

  coloured light when in a flame because the electrons absorb energy  and move from one shell (or energy level) to another higher energy level further from the nucleus 

   = (known as electrons being ‘excited’ and ‘jumping up’) 
• when do electrons 'drop back down' to their normal shell?

  when they are in a higher energy level as they are unstable, emitting a certain amount of energy in the form of light
• why can electrons 'jump out' at different times

  because different colours are produced from different elements
• if an electron absorbs a lot of energy > higher jump (eg. 3 shells) 


  it would then give off a lot of energy when it 'falls back down' and equate light of a SHORTER wavelength.
• smaller jump (eg. 1 shell)

  would equate to a smaller amount of energy being emitted when it falls back down and a LONGER/LOWER wavelenth
• emission spectrum 


  pattern of coloured lines on a black background

  emission spectra are unique for each element
• what does emission line show?

  specific wave of light being emitted due to atoms being heated and electrons emitting energy as light as they fall back down to their energy levels
• Ion 


  the change in number of electrons in an atom
• atom loosing electrons 


  positive ion (more protons than electrons)
• atom gaining electrons 


  negative ion (more electrons than protons)
• non-metals are...

  electron acceptors
• metals are...

  electron donors
• anion


  negative ion
• cation 


  positive ion
• gaining electrons 


  non - metals
• losing electrons 


  metals
• half equation for metals

  metal atom -> metal ion + electrons
• half equation for non-metals

  non-metal atom + electrons -> non-metal ion
• in metals, going down agroup 1 & 2, number of electrons..

  increases
• in non-metals, going down group 17, number of electrons...

  increases
• atomic radius increases or decreases in metals

  increases
• atomic radius increases or decreases in metals

  increases