topic 1 - atoms

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Topic 1 - Atomic structure and the periodic table

Atoms

Atoms contain protons, neutrons and electrons.

the nucleus-

  • in the middle of the atom
  • contains protons and neutrons 
  • positive charge (becuase of protons)
  • whole mass of atom is in the nucleus  

the electrons-

  • move around nucleus is shells (2,8,8...)
  • negatively charged
  • virtually no mass
  • particle   relative mass   relative charge 

proton                    1                      +1

neurton                  1                        0

eletron                    very small         -1

number of protons equals the number of electrons-

  • atoms are neutral (no overall charge unlike ions)
  • this is because there is the same number of protons as there is electrons
  • in an ion the protons and electrons dont equal the same (has an overall charge)

atomic number & mass number-

  • atomic number = amount of protons
  • mass number = total number of rotons and neutrons

eg

23 - mass number

    Na - element 

 11 - atomic number 

elements-

  • elements consist iof atoms with the same atomic munber
  • its number pof protons decides which type of atom its is 
  • eg an atom with only one proton in its nucleus is hydrogen.

isotopes-

  • differnt forms of an element, same numver of protons, differnt number of neutrons.
  • eg carbon 12 has 6 protons, 6 electrons and 12 neutrons.

          carbon 13 has 6 protons, 6 electrons BUT 13 neurtons.

  • relative atomic mass = (sum of isotope abundance X isotope mass number) 
  •                                                   sum of abundances of all isotopes 

compounds-

  • atoms join together to form compounds when they react with one another, held together by chemical bonds. 
  • making bonds involves giving away, taking or sharing electrons.
  • a compound formed from a metal and non metal is done through ionic bonding. this is where the metal atoms lose electrons becoming positively charged and the non metals gain electrons becoming negativeky charged. 
  • opostite charges mean that they are strongly attracted to eachother.
  • a compound formed from non metals conatin monocules - this is throigh covalent bonding where each atom shares an electron with another atom.
  • in order to form compounds each atom must be left with a full outer shell of electrons.
  • the properties of a compound are usually totally different to the origional element.

formulas & equations-

  • elements are represented by symbols - compounds are represented by formulas 
  • eg CO2 - 1 carbon atom, 2 oxygen atoms > carbon dioxide 
  • chemical changes are shown usuing chemical equations.
  • eg  methane + oxygen > carbon dioxide + water 
  •             ( reactants )          

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