2. The PTE
•The PTE was first
developed by
Russian, Dmitri
Mendeleev
Mendeleev, the man,
the myth, the legend
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
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. 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. 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. 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. 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. 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. Group II – The
Alkaline Earth Metals
•Harder than Gr I
•Tarnish quickly
•Less reactive than Gr I
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. 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. Group II
•Like Gr I, they have
characteristic flame
colours (Table 3.9)
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. 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. 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. 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. 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
