Chemistry Knowledge organiser – Unit 1 Atomic Structure J.J Thomson Plum Pudding Bohr's Model of the Atom The Development of the Dmitri Mendeleev Electronic Configuration Model In 1913, Neil Bohr explained that the Periodic Table Mendeleev discovered the periodic table while attempting to By looking at the periodic table we know how many protons, As the atom is so small, were not in a cloud, but on energy levels orbiting In the past, masses were used by organise the elements in February of 1869. He did it by writing the neutrons and electrons each element has. people found it hard to the nucleus at different distances (a bit like the scientists trying to organise the properties of the elements on pieces of card and arranging and In Chemistry, we need to know where we find the electrons. understand the way it was solar system model we have). elements. This was mainly because the rearranging them until he realised that, by putting them in order Electronic configuration – are the diagrams we draw to show structured. idea of atoms being made up of of increasing atomic weight, certain properties of elements where the electrons are. These are important in helping us to Bohr's Idea - The negative electrons are in orbit smaller sub-atomic particles had not regularly occurred. understand how the atoms bond together to make compounds. The first person who around the nucleus in shells and are kept in orbit been developed. discovered electrons, Sir J.J by the pull of the protons. Not only did Mendeleev arrange the elements in the correct way, Surrounding the positive nucleus are the negative Thomson, put forth his 'Plum but if an element appeared to be in the wrong place due to its Johan Dobereiner electrons. Pudding' Model of an atom. James Chadwick and Discovery of Neutrons atomic weight, he moved it to where it fitted with the pattern he In 1829, Johann Döbereiner recognised However, they are not randomly placed, but have He believed that the atom With the discovery of protons, neutrons and had discovered. triads (threes) of elements with specific places they can occupy. was a sphere with a positive electrons, physicists could put forth a diagram of chemically similar properties, such as These are called shells, levels or orbitals – charge and had electrons an atom. They could explain that an atom is made The real genius of Mendeleev’s achievement was to leave gaps for , and , and they all mean the same thing – the place where stuck inside it. up of electrons, neutrons and protons. undiscovered elements in groups where he predicted they would showed that the properties of the electrons are found. have similar properties to the other elements in that . middle element could be predicted The electron levels can only hold a set number of The centre of an atom is the nucleus that contains Within 15 years, three of these elements were discovered and from the properties of the other two. electrons. protons and neutrons. This makes the nucleus Mendeleev’s predictions were shown to be incredibly accurate. The first – closest to the nucleus – fills first and can positively charged. The electrons are present on John Newlands hold up to 2. different shells or orbits that revolve around the Newlands noticed that there were The second – fills next and can hold up to 8. Rutherford's Atomic Model nucleus. similarities between elements with The third – fills next and can hold up to 8. Ernst Rutherford was atomic weights of + or - 7. He called The fourth – fills next and can hold up to 18. studying radioactive this The Law of Octaves. Newlands did (Luckily for us we only have to ever put on 2!) substances. Through his not leave any gaps for undiscovered experiment of hitting foil elements in his table, and sometimes had to cram two elements into one with alpha particles he found If you look there are: box in order to keep the pattern. that most of the alpha 2 on the first particles passed through the 8 on the second gold foil – he suggested that 8 on the third the atom was mostly made up has the lowest boiling 2 on the fourth of empty space. point of group 0. The trend shows Electronic configurations for the first THREE noble We can write this as 2, 8, 8, 2 that the boiling point increase gases are: Next he observed that some It tells us the information above, alpha particles were deflected down the group. without the need for a diagram. through small and large angles. This proved that there was a 'centre of positive charge' in an atom. Rutherford proved that the They all have full outer shells and as a result are nucleus was positively charged. The nucleus is very INERT (unreactive with other elements). They exist small, dense and hard when as single atoms. compared to the whole atom. The Group 0 – Noble Gases Relative Atomic Masses Group 0 are all gases. 23 is the of sodium. This is called the relative He, Ne, Ar, Kr, Xe, Rn atomic mass. Relative is because the protons and neutrons are too small to weigh individually. Uses of the noble gases It is also an average of all the of sodium.

Use in welding to

prevent the metal reacting with in the air. – This is an element with the same number of protons – but a different number The electronic configurations shows us: of neutrons in its nucleus. The Group number = number of outer electrons If you look at on the periodic table its RAM is 35.5 this is because it exists as the The number = number of electron shells.

two isotopes of:

How do the Group 7 react? How do the Group 1 metals react with chlorine, 1. Describe the position, charge and mass of a proton. oxygen and water? 2. Describe the position, charge and mass of a neutron. Reaction Lithium Sodium potassium 3. Describe the position, charge and mass of an With oxygen Burns red Burns more Burns electron. flame vigorously with violently with 4. How many elements are in CaCO3? yellow flame lilac flame 5. How many atoms are in CaCO3? 6. What is a mixture? White ash of White ash of 7. Why can’t compounds be separated by White ash of sodium oxide potassium physical processes? The trend show an increase in the melting and boiling points of the halogens as the lithium oxide oxide 8. What does distillation separate? size of the atom increase. With water Floats, fizzes Floats and melts Floats, 9. What can crystallisation separate? producing , fizzes producing gas 10. What can Filtration separate? Formula State Colour hydrogen gas, hydrogen gas, sets on fire 11. Who came up with the plum pudding theory? F2 Gas Pale yellow produces produces with lilac 12. Who came up with the idea of electron shells? Chlorine Cl2 Gas Green colourless colourless flame, 13. Who discovered protons in the nucleus? Br2 Liquid Red lithium sodium produces 14. What did Rutherford discover? I2 Solid Purple hydroxide hydroxide colourless 15. How did he discover it? At2 Solid Grey solution solution potassium 16. Why are atoms neutral? (alkali) hydroxide 17. What is an ion? Halogens will dissolve in water to produce acidic solutions solution 18. Why do ions form? eg hydrochloric acid 19. What are isotopes? 20. How many neutrons are in -14? What do all Group 1 elements have in common? Halogens will react with nitrate to produce coloured precipitates. They all have one outer electron. 21. Where can you find the number of protons in an atom? Colour of Equation 22. What is the number of electrons equal to? precipitate 23. What is the max number of electrons in each when silver shell? nitrate is The reactivity INCREASES down the group: 24. Draw the electron structure of ? added More shielding of the nucleus 25. What does the group number tell you about Outer electron is easier to remove releasing more energy as heat. Potassium white AgNO3 + KCl  AgCl (s) + KNO3 an atom’s electron structure? chloride 26. What do all group 0 elements have in 3  (s) 3 Potassium cream AgNO + KBr AgBr + KNO common? bromide Equations: 3  (s) 3 27. Why are group 1 elements so reactive? Potassium yellow AgNO + KI AgI + KNO Lithium + oxygen  Lithium oxide iodide 28. Why are group 7 elements so reactive? 4Li + O2  2Li2O 29. What is the general equation for a group 1 Lithium + chlorine  lithium chloride Halogens will displace a less reactive halogen from a solution. metal reacting with water? 2Li + Cl2  2LiCl Lithium + water  lithium hydroxide + hydrogen 30. What do all of the formulas of group 7 2Li + H2O  2LiOH + H2 elements have in common. This is the reaction pattern for all group 1 – just change the name and symbol 31. Describe the trend in reactivity as you go  down group 1. 32. Why does this trend exist? 33. Describe the reactivity trend as you go down group7 Equations 34. Why does this trend exist? Chlorine + potassium  Potassium + Bromine bromide Chloride 35. What will a more reactive halogen do to a less Cl2 + 2KBr  2KCl + Br2 reactive one?