atomic structure and the periodic table

• Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.
• The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it
• The results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model.
• Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations
• Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles.
• The experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. This was about 20 years after the nucleus became an accepted scientific idea.
• what is filtration used for?

  filtration is used to seperate an insoluble solid from a liquid
• how do we carry out fractional distallation?

  1 we heat our solution to evaporate the liquid turning it into a vapour 2. we cool the vapour to condense it back to a liquid

  
• what is in a nuclear model?

  in a nuclear model, most of the atom is simply empty space in the centre we have a positive nucleus which contains most of the mass of the atom around the edge, we find negative electrons
• what does abundance mean?


  the word abundance means how common each isotope is
• how do you calculate relative atomic mass?

  relative atomic mass= (mass number of isotope 1 x percentage abundance of isotope 1) +(mass number of isotope 2 x percentage abundance of isotope 2) / 100

  
• how many energy levels are there of an element?

  there are 3 and they are shown like this 2,8,8
• how did Mendeleev arrange the periodic table?

  started by arranging all the elements in order of increasing atomic weights. he switched the orders of specific elements so that they fitted the patterns of other elements in the same group.
• Mendeleev realised that some elements had not been discovered yet. so he left gaps in his periodic table.
• Mendeleev predicted the properties of the undiscovered elements based on other elements in the same group.
• the noble gases are very unreactive elements
• neon in the group 0 has a full energy level as it has 10 electrons 2,8
• argon has 18 electrons and has 2,8,8 it has a full outer energy level which makes it unreactive
• all elements in group 0 have a full outer energy level which makes them unreactive
• all of the group 0 elements have boiling points lower than room temperature
• the boiling point of the noble gases increase, as the relative atomic mass increases.
• highly reactive metals are found in groups 1,2
• the transition metals are generally less reactive than group 1 and 2 metals
• when metals react they lose electrons to gain a full outer energy level
• when metals react and lose electrons to gain a stable energy level this gives them the stable electronic structure of a group 0 noble gas
• if the metal does not become stable when it reacts it becomes an ion
• metals always form positive ions
• group 1 metals are soft
• when lithium reacts with oxygen what happens?


  when lithium is cut with a scalpel and exposed to air, it reacts rapidly with oxygen in the ai, forming the compound lithium oxide.
• what happens when sodium reacts with oxygen?


  when sodium gets cut with a scalpel, it reacts with oxygen to produce sodium oxide. sodium reacts more rapidly than lithium
• what happens when potassium reacts with oxygen?


  it forms the compound potassium oxide, potassium reacts even more rapidly with oxygen than lithium or sodium.
• as you go down group 1 elements, do they react more rapidly with oxygen or not?


  yes they do as you go down group 1, the reactivity of the metals increase as they get more rapid
• when lithium reacts with oxygen the outer energy level from the lithium atom moves to the oxygen atom. which causes the lithium atom to have a full outer energy level.
• what happens when group 1 metals react with oxygen?

  they all become metal oxides

  
• what happens to lithium when it reacts with water?

  the lithium reacts rapidly with water and before we add universal indicator turning the water green. we can then see effervescence or fizzing which tells us that a gas is being produced and the universal indicator turns purple, showing us that a alkaline solution has been produced
• what happens to sodium when it reacts with water?

  a gas produced and an alkaline solution forming and fizzing or bubbling
• what happens when potassium reacts with water?

  when potassium reacts with water, the reaction is extremley rapid which shows that light is being produced and a flame is formed and an alkaline solution as well as a gas being produced.
• as we go down group 1, the radius of the atom increases which means that there is a greater distance between the positive nucleus and the negative outer electron.