Bell work: Think about what we did on Friday. Explain what an “energy level” is. Is it related to electron shells? What happens when an electron “drops down” an energy level? What is needed for an electron to “move up” an energy level?

FINISHING UP THE LAB FROM FRIDAY We will view Helium and I want you to draw what you observe. We will view Helium and I want you to draw what you observe. I want the lab write-up handed in by Friday September I want the lab write-up handed in by Friday September

PERIODIC TRENDS SCH3U – Mr. Gavranic

TIMMY’S WORLD

PERIODIC TABLE The periodic table is an extremely well organized tool from which a great deal can be learned simply by observation. The periodic table is an extremely well organized tool from which a great deal can be learned simply by observation. We will learn about the following trends… We will learn about the following trends… Atomic Radius Atomic Radius Ionization Energy Ionization Energy Electronegativity Electronegativity Electron Affinity Electron Affinity

ATOMIC RADIUS The radius of an atom is the distance from the center of the nucleus to the outermost electrons (the valence electrons) The radius of an atom is the distance from the center of the nucleus to the outermost electrons (the valence electrons) The larger the atom, the larger its atomic radius (sometimes called atomic size) The larger the atom, the larger its atomic radius (sometimes called atomic size)

ATOMIC RADIUS Why does the atomic radius increase as you go down the table or to the left? (think about what the period numbers and the family numbers mean) Why does the atomic radius increase as you go down the table or to the left? (think about what the period numbers and the family numbers mean) As you go down the table… As you go down the table… The radius increases because you are adding more shells. Remember, the number of the period means more shells. The radius increases because you are adding more shells. Remember, the number of the period means more shells. There is also the added effect of electron shielding. There is also the added effect of electron shielding. Electron Shielding: each time a new shell is added, the negative charge of the electrons in the inner shells offers a force of repulsion on the valence electrons Electron Shielding: each time a new shell is added, the negative charge of the electrons in the inner shells offers a force of repulsion on the valence electrons As you go to the right… As you go to the right… There is an increasing number of protons. There is an increasing number of protons. Each added proton has a greater effect than each added electron. Therefore, the result is each electron being pulled closer to the nucleus and the radius decreasing. Each added proton has a greater effect than each added electron. Therefore, the result is each electron being pulled closer to the nucleus and the radius decreasing. The effect of adding more protons is very strong The effect of adding more protons is very strong

DISCUSSION AND INQUIRY Would Na or Br have a larger radius? Why… Would Na or Br have a larger radius? Why… Which is the smallest atom? Which is the largest? Why… Which is the smallest atom? Which is the largest? Why… Rank the following 2 lists in order of increasing radius Rank the following 2 lists in order of increasing radius Li, Al, Br, F, Cs, Ca Li, Al, Br, F, Cs, Ca Na, O, C, Xe, Fr Na, O, C, Xe, Fr

DISCUSSION AND INQUIRY Would Na or Br have a larger radius? Why… Would Na or Br have a larger radius? Why… Na would have a bigger radius. Yes, Bromine does have an extra electron shell, but it also has 24 more protons. The effect of adding this many more protons out ways the effect of having an extra shell. The electrons in the 1 extra shell are pulled so much stronger by the nucleus. Na would have a bigger radius. Yes, Bromine does have an extra electron shell, but it also has 24 more protons. The effect of adding this many more protons out ways the effect of having an extra shell. The electrons in the 1 extra shell are pulled so much stronger by the nucleus.

DISCUSSION AND INQUIRY Which is the smallest atom? Which is the largest? Why… Which is the smallest atom? Which is the largest? Why… Helium is the smallest atom, it only has 1 shell…2 electrons being pulled very strongly by 2 protons Helium is the smallest atom, it only has 1 shell…2 electrons being pulled very strongly by 2 protons Francium is the largest atom, it has the largest number of shells and the fewest number of protons in it’s period. Francium is the largest atom, it has the largest number of shells and the fewest number of protons in it’s period. Side note: though you could say Cs is the largest stable atom Side note: though you could say Cs is the largest stable atom

DISCUSSION AND INQUIRY Rank the following 2 lists in order of increasing radius Rank the following 2 lists in order of increasing radius Li, Al, Br, F, Cs, Ca  F, Br, Al, Li, Ca, Cs Li, Al, Br, F, Cs, Ca  F, Br, Al, Li, Ca, Cs Na, O, C, Xe, Fr  O, C, Na, Xe, Fr Na, O, C, Xe, Fr  O, C, Na, Xe, Fr

IONIZATION ENERGY Ion: an atom (or molecule) in which the number of protons (atomic number) does not match the number of electrons. Ion: an atom (or molecule) in which the number of protons (atomic number) does not match the number of electrons. Example: Carbon-12 and Carbon-14. These are both Carbon, but one has 12 electrons, the other has 14. Example: Carbon-12 and Carbon-14. These are both Carbon, but one has 12 electrons, the other has 14. Ionization Energy: the minimum amount of energy required to remove an electron Ionization Energy: the minimum amount of energy required to remove an electron First Electron Ionization Energy: the ionization energy to remove the first electron off an atom First Electron Ionization Energy: the ionization energy to remove the first electron off an atom

IONIZATION ENERGY The ionization energy increases as you go UP and to the RIGHT on the periodic table The ionization energy increases as you go UP and to the RIGHT on the periodic table The larger the ionization energy, the more difficult it is to rip away one of that atom’s electrons. The larger the ionization energy, the more difficult it is to rip away one of that atom’s electrons.

DISCUSSION AND INQUIRY Which element has the highest First Ionization Energy? Which has the lowest? Which element has the highest First Ionization Energy? Which has the lowest? Why… Why… Do you think the second ionization energy would be greater or lesser than the first? Why… Do you think the second ionization energy would be greater or lesser than the first? Why… Cesium is one of the most reactive elements on the periodic table. Why do you think that is? Cesium is one of the most reactive elements on the periodic table. Why do you think that is?

DISCUSSION AND INQUIRY Which element has the highest First Ionization Energy? Which has the lowest? Which element has the highest First Ionization Energy? Which has the lowest? Highest -- Helium Highest -- Helium Lowest – Francium Lowest – Francium Why… Why… Helium, 2 protons, 2 electrons, 1 shell. Helium, 2 protons, 2 electrons, 1 shell. Francium…small number of protons to the number of shells Francium…small number of protons to the number of shells

DISCUSSION AND INQUIRY Do you think the second ionization energy would be greater or lesser than the first? Why… Do you think the second ionization energy would be greater or lesser than the first? Why… The second ionization energy is always greater than the first because of simple math. Once you take one electron away, you have the same number of protons holding onto a smaller number of electrons. The second ionization energy is always greater than the first because of simple math. Once you take one electron away, you have the same number of protons holding onto a smaller number of electrons.

DISCUSSION AND INQUIRY Cesium is one of the most reactive elements on the periodic table. Why do you think that is? Cesium is one of the most reactive elements on the periodic table. Why do you think that is? It has such a high ionization energy. Reactions between elements, as you’ve learned, are all about the exchange of valence electrons. Cs really wants to give away its outer electron. It has an extremely weak hold on it. It has such a high ionization energy. Reactions between elements, as you’ve learned, are all about the exchange of valence electrons. Cs really wants to give away its outer electron. It has an extremely weak hold on it.

ELECTRON AFFINITY Electron Affinity: the change in energy of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion. Electron Affinity: the change in energy of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion. Electron affinity: essentially it describes the ability of an atom to accept an electro Electron affinity: essentially it describes the ability of an atom to accept an electro Example: F has a really high electron affinity because is in a high energy state, it wants an electron to drop down to the stable, low energy state of a noble gas Example: F has a really high electron affinity because is in a high energy state, it wants an electron to drop down to the stable, low energy state of a noble gas

ELECTRON AFFINITY Electron affinity increases as you go UP and to the RIGHT of a periodic table Electron affinity increases as you go UP and to the RIGHT of a periodic table The bigger the magnitude of the electron affinity of the atom, the more easily it can accept an electron The bigger the magnitude of the electron affinity of the atom, the more easily it can accept an electron

DISCUSSION AND INQUIRY Which atoms have the highest and lowest electron affinities? Which atoms have the highest and lowest electron affinities? Why do you think that is… Why do you think that is… Why does electron affinity increase UP and to the RIGHT? Why does electron affinity increase UP and to the RIGHT? Explain why Cs ionization energy is so high yet its electronegativity is so low? Does it hate electrons? Why does it want to get rid of them so badly? Explain why Cs ionization energy is so high yet its electronegativity is so low? Does it hate electrons? Why does it want to get rid of them so badly?

CHEMIAL REACTIVITY METAL reactivity increases DOWN and to the LEFT METAL reactivity increases DOWN and to the LEFT NON-METAL reactivity increases UP and to the RIGHT NON-METAL reactivity increases UP and to the RIGHT

ELECTRONEGATIVITY Electronegativity: describes an atom’s tendency to want to attract electrons toward itself Electronegativity: describes an atom’s tendency to want to attract electrons toward itself Essentially, the HIGHER the electronegativity, the more the atom WANTS an electron. Essentially, the HIGHER the electronegativity, the more the atom WANTS an electron.

ELECTRONEGATIVITY The electronegativity of an element increases as you go UP and to the RIGHT of the periodic table The electronegativity of an element increases as you go UP and to the RIGHT of the periodic table

FINAL SUMMARY OF TRENDS Explain… Explain… Why does atomic size increase DOWN and to the LEFT along the periodic table Why does atomic size increase DOWN and to the LEFT along the periodic table Why does ionization energy increase UP and to the RIGHT along the periodic table Why does ionization energy increase UP and to the RIGHT along the periodic table Why does electronegativity increase UP and to the RIGHT along the periodic table Why does electronegativity increase UP and to the RIGHT along the periodic table Why does electron affinity increase UP and to the RIGHT along the periodic table? Why does electron affinity increase UP and to the RIGHT along the periodic table?

1. Who discovered the atom? 2. What was Rutherford’s contribution to the understanding of matter? 3. Explain the difference between ground state and excited state. 4. Explain the gold foil experiment. How did it prove the existence of a positive nucleus? 5. Explain the Hydrogen Emission Spectrum. What are those coloured bands and where do they come from? 6. We’ve looked at emission spectra where we excite gas and look at the light given off. What do you think an absorption spectrum would look like – where we look at white light being shone through a cold gas (like H for example)