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# The periodic table

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### The periodic table

1. 1. The Periodic Table
2. 2. The PTE •The PTE was first developed by Russian, Dmitri Mendeleev Mendeleev, the man, the myth, the legend
3. 3. •Mendeleev made up his table by ordering the elements by increasing mass and grouped them according to similar properties. •He left gaps for as yet undiscovered elements • He was able to predict their properties as well (color, MP, density, weight, etc) • Successfully predicted 7 out of 10
4. 4. Mendeleev’s PTE
5. 5. •Columns are known as Groups or Families •Rows are known as Periods •The elements are arranged according to increasing atomic number (Z)
6. 6. Group I – The Alkali Metals Video Link
7. 7. Group I – The Alkali Metals •Good conductors of heat and electricity •Soft •Low density (float on water) •Dull quickly when cut •Low Melting points
8. 8. A word about equations: • Law of constant composition – Compounds always have the same elements joined together in the same proportions. • Balanced Chemical Equations • Formulae of reactants and products • Relative number of particles involved • Physical state (s), (l), (g), (aq) • Same number of each type of atom on both sides of the equation
9. 9. Alkali Metal Reactions Gr I Reactions Burn in oxygen Lithium burns with Oxygen to form lithium oxide (Li2O) Write and Balance the equation. 4Li(s) + O2(g) -> 2Li2O(s) Write the balanced equation for the reaction between Sodium and Oxygen to form sodium oxide (Na20). 4Na(s) + O2(g) -> 2Na2O(s)
10. 10. Alkali Metal Reactions •Gr I Reactions •Burn in oxygen cont… •Group 1 oxides dissolve in water to form alkaline solutions of the metal hydroxide. •Li2O(s) + H20(l) -> 2LiOH(aq) •What would happen when sodium oxide is dissolved in water? •Na2O(s) + H20(l) -> 2NaOH(aq)
11. 11. Alkali Metal Reactions• Gr I Reactions • React vigorously with water • Potassium reacts with water to form potassium hydroxide (KOH) and hydrogen. • Write the balanced equation. • 2K (s) + 2H2O (l)  2KOH (aq) + H2(s) • KOH forms an alkaline (basic) solution with turns pink/purple when Phenolphthalein is present. • Write the balanced equation for sodium reaction with water to form sodium hydroxide (NaOH) and hydrogen gas. • 2 Na (s) + 2 H2O (l) > 2 NaOH (aq) + H2(g)
12. 12. Alkali Metal Reactions • React vigorously with the halogens • Sodium reacts with Chlorine to produce sodium chloride (NaCl). Write the balanced equation. • 2Na + Cl2  2NaCl • Look at the Bohr model for sodium. What about Chlorine? Why do you think sodium is so reactive with chlorine so vigorously? b/c of the lone e- in the outer shell • More reactive as you go down the group. Why? b/c the electrons are farther away from the nucleus, easier for them to be given away.
13. 13. Group II – The Alkaline Earth Metals •Harder than Gr I •Tarnish quickly •Less reactive than Gr I
14. 14. Group II Reactions •Reaction with oxygen •Magnesium reacts with oxygen to form Magnesium oxide. •2Mg + O2  2MgO •What happens when Calcium reacts with oxygen? •2Ca + O2  2CaO
15. 15. Group II Reactions • Reaction with the halogens • Magnesium reacts with chlorine to form Magnesium chloride. • 2Mg + Cl2  2MgCl • More reactive as you go down the group. Why? Valence electrons are farther away from attractive force of the nucleus. • Less Reactive than Group I b/c its harder for the atom to give up 2 electrons than just one.
16. 16. Group II •Like Gr I, they have characteristic flame colours (Table 3.9)
17. 17. Group VII – The Halogens
18. 18. Group VII – The Halogens •Halogen means “salt former” ie. NaCl •F, Cl, Br, I, At (radioactive) •Colours get darker going down the group
19. 19. Group VII – The Halogens
20. 20. Group VII – The Halogens •g  l  s as you go down •Reactivity decreases as you go down. (Note this reactivity trend is opposite than groups I and II) Why?
21. 21. As we go down the group, the atomic radius increases because there are more electrons. These layers of electrons shield the positive nucleus and make it is harder for the atom to attract an 8th electron to fill its outer shell.
22. 22. Group VII – The Halogens Reactions: •Halogens form acids with hydrogen Examples: HF, HCl, HBr, HI •They displace halogens below them (lab) Example Reaction: 2KBr + Cl2  2KCl + Br2
23. 23. Group VII – The Halogens Uses: •F is used in toothpaste •Cl is in bleach, PVC (polyvinyl chloride) •Br is in medicines and fire retardants •I is used in disinfectants
24. 24. Group 0 – The Noble Gases •Colourless •Virtually unreactive “monatomic” (Xe and Kr have been known to form compounds) Why? •Ar is used in light bulbs to protect the W filament •Neon is used in neon signs
25. 25. Group 0 – The Noble Gases Neon Signs
26. 26. The Transition Metals •Much harder and denser than Groups I and II •High MP (except Hg) •Less reactive •Great catalysts (speed up reactions)
27. 27. Hydrogen •A non-metal that can act as a metal •Usually grouped with Gr I or Gr VII