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How do you know how many atoms and how many elements are in a symbol equation?

How do you know how many atoms and how many elements are in a symbol equation?. CO 2. Tells you how many ELEMENTS there are (an easy way to do this is to count the capital letters). The number tells you how many ATOMS of each of that element there is. Have a go….

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How do you know how many atoms and how many elements are in a symbol equation?

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  1. How do you know how many atomsand how many elements are in a symbol equation? CO2 Tells you how many ELEMENTS there are (an easy way to do this is to count the capital letters) The number tells you how many ATOMS of each of that element there is

  2. Have a go… How many atoms and elements are in... • H2O • CaCO3 • 2MgO • 2CaCl2 • Mg(NO3) 2 Everything is multiplied by this number Everything in the bracket is multiplied by this number

  3. Fractional distillation – separates liquids with different boiling points Condenser • Filter paper • Funnel • Conical flask Filtration -separates fine, insoluble particles from a liquid Chromatography – separates a mixture of chemicals / dyes • Evaporating dish • Bunsen burner • Tripod • Gauze Fractional distillation – separates liquids with different boiling points Evaporation / crystallisation – separates liquid from a dissolved substance

  4. Order of discovery of sub atomic particles

  5. Rutherford Experiment: the set up Geiger and Marsden counted the tiny green flashes in the microscope produced when alpha particles hit the screen. Both Geiger and Marsden described this as one of the most difficult and boring experiments they’d ever had to do. Moveable Microscope Zinc sulphide screen (glows when hit by alpha particles) Shield Source of alpha particles Vacuum (air pumped out) Very thin gold foil

  6. Geiger and Marsden placed the microscope as shown. As expected, most of the alpha particles went straight through A few alpha particles were scattered by angles less than 90º, also as expected.

  7. Much to their surprise, a very small number of alpha particles (about 1 in 8000) bounced off the gold atoms! Under protest, Geiger and Marsden placed the microscope behind the gold leaf. They handed the results to Professor Rutherford who now had to explain what was going on.

  8. Observations Rutherford’s experiment finished with 3 observations. You need to explain what each observation tells us about the atom as we know it today • Most of the fast, highly charged alpha particles went whizzing straight through un-deflected. • Some of the alpha particles were deflected through a small angles • A very small number of alpha particles were deflected backwards!

  9. Conclusions Most of the fast, highly charged alpha particles went whizzing straight through undeflected. SUGGESTS THAT MOST OF THE ATOM IS EMPTY SPACE!!

  10. Conclusions Some of the alpha particles were deflected through a small angles! SUGGESTS THAT THERE IS A CONCENTRATED POSITIVE MASS SOMEWHERE IN THE ATOM.

  11. Conclusions A very small number of alpha particles were deflected backwards! SUGGESTS THAT THE CONCENTRATED MASS IS MINISCULE COMPARED TO THE SIZE OF THE REST OF THE ATOM, BUT CONTAINS MOST OF THE MASS

  12. What did Bohr do? (1913) • Realised that electrons should be attracted in to the nucleus • Used mathematical models to show that electrons occupy fixed energy levels (or shells) around the nucleus

  13. Plum Pudding Model Nuclear Model • Compare the differences between the plum pudding model and the nuclear model. • Think about the location of: • The mass • The negative charge • The positive charge • The density

  14. nucleus electron neutron proton The atom Draw a labelled diagram of the atom showing the nucleus and labelling protons, neutrons and electrons. The overall charge on an atom is 0… what does this tell you about the number of protons and electrons? 1 +1 1 0 1/2000 (Very small) -1

  15. Atoms are very small, having a radius of about 0.1 nm (1 x 10-10m) How big is an atom? The radius of a nucleus is less than 1/10 000 of that of the atom (about 1 x 10-14m)

  16. What does this show you? Atomic Mass number (show the number of protons and neutrons in the nucleus) (number of neutrons = top number – bottom number) 12 C 6 Carbon Atomic number (tells you the number of protons and the number of electrons) How do we calculate mass and atomic numbers?

  17. Isotopes Isotopes are atoms of the same element (same protons & electrons) with different numbers of neutrons. This makes them unstable. Hydrogen Deuterium Tritium 1 2 3 H H H 1 1 1

  18. To calculate the RAM of a mixture of isotopes, multiply the percentage of each isotope by its atomic mass and add them together. RAM of chlorine= (75% x 35) + (25% x 37) = (0.75 x 35) + (0.25 x 37) = 26.25 + 9.25 = 35.5 Isotopes and RAM Many elements are a mixture of isotopes. The RAM given in the periodic table takes account of this. For example, chlorine exists as two isotopes:chlorine-35 (75%) and chlorine-37 (25%).

  19. Electronic structure Chlorine Calcium Argon xx xx xx xx x x xx xx xx xx Cl xx xx x xx xx x Ca x x xx xx x x xx 2,8,7 2,8,8,2 2,8,8 Only a certain number of electrons can fit in each ‘shell’. 2 in the first shell 8 in the second shell 8 in the third shell

  20. Group number= how many electrons in the outer shell Nobel gases Alkali Metals Period number =how many shells the atom has Halogens Transition Metals

  21. Development of the Periodic table John Newlands (1865) – • Arranged elements in order of atomic weights (realised every 8th element had the same properties) • Didn’t leave gaps so only really worked up until calcium • Had lots more dissimilar elements in a column Dmitri Mendeleev (1869) – • Left gaps for undiscovered elements • Changed the order of some elements so they fit with the properties • Elements with the predicted properties eventually discovered

  22. What is an ION? Video • An ION is a ‘charged’ particle. • Atoms 'like' to have a full shell of electrons. They are more stable if they have a full electron shell. Atoms will lose or gain electrons in order to gain a full shell. • It has therefore either LOST or GAINED electrons.

  23. Click on me!! Remember that the proton number tells you how many protons or electrons the atom has. Not any more!!! Why not??

  24. An ion is shown like this to show the electron shells Or simply like this

  25. Total charge = +1 Total charge = 0 + one electron is lost Na Na Electron arrangement: [2.8]+ (full outer shell) The sodium ion Sodium ion: Sodium atom: 11 protons = +11 11 protons = +11 10 electrons = -10 11 electrons = -11 Electron arrangement: 2.8.1 (partially full outer shell)

  26. Total charge = +2 Total charge = 0 2+ two electrons are lost Mg Mg Electron arrangement: [2.8]2+ (full outer shell) The magnesium ion Magnesium ion: Magnesium atom: 12 protons = +12 12 protons = +12 10 electrons = -10 12 electrons = -12 Electron arrangement: 2.8.2 (partially full outer shell)

  27. chlorine atom = 2.8.7 chloride ion = Cl- (not Cl1-) oxide ion = O2- oxygen atom = 2.6 nitrogen atom = 2.5 nitride ion = N3- Negative ions An atom that gains one or more electrons forms a negative ion. Non-metal atoms, such as chlorine, oxygen and nitrogen,form positive ions. Negative ions have a small ‘-’ symbol and a number by them to indicate how many electrons they have gained to fill their outer shell. For example: The name of the ion is slightly different to that of the atom – it ends ‘–ide’.

  28. Total charge = - 1 Total charge = 0 - one electron is gained F F Electron arrangement: [2.8]- (full outer shell) The fluoride ion Fluoride ion: Fluorine atom: 9 protons = +9 9 protons = +9 10 electrons = -10 9 electrons = -9 Electron arrangement: 2.7 (partially full outer shell)

  29. Total charge = - 2 Total charge = 0 2- two electrons are gained S S Electron arrangement: [2.8.8]2- (full outer shell) The sulfide ion Sulfide ion: Sulfur atom: 16 protons = +16 16 protons = +16 18 electrons = -18 16 electrons = -16 Electron arrangement: 2.8.6 (partially full outer shell)

  30. AN ATOM WITH A POSITIVE OR NEGATIVE CHARGE IS CALLED AN ION!!!! • Complete the table to show how each of the following atoms can become stable and what will be the charge on the ion?

  31. Group 0

  32. Group 1 (alkali) metals More reactive Higher melting point

  33. metal oxygen metal oxide Metals and oxygen – general equation Potassium and sodium are metals that react vigorously with water even when a small amount of each metal is used. Lithium + oxygen  Lithium oxide Li + O2  Li2O Sodium + oxygen  ________ _______ Na + O2  Na2O Potassium + oxygen  ________ ______ K + O2  K2O

  34. metal chlorine metal chloride Metals and chlorine – general equation Potassium and sodium are metals that react vigorously with chlorine even when a small amount of each metal is used. Lithium + chlorine  Lithium chloride 2Li + Cl2  2LiCl Sodium + chlorine ________ _______ 2Na + Cl2  2NaCl Potassium + chlorine ________ ______ 2K + Cl2  2KCl

  35. metal water metal hydroxide hydrogen Metals and water – general equation Potassium and sodium are metals that react vigorously with water even when a small amount of each metal is used. Lithium + Water  Lithium Hydroxide + Hydrogen 2Li + 2H2O  2LiOH + H2 Sodium + Water  ________ _______ + Hydrogen 2Na + 2H2O  2NaOH + H2 Potassium + Water  ________ ______ + _______ 2K + 2H2O  2KOH + H2

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