The periodic table

The Periodic Table

The PTE•The PTE was first developed by Russian, Dmitri Mendeleev

Mendeleev, the man, the myth, the legend

•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

Mendeleev’s PTE

•Columns are known as Groups or Families

•Rows are known as Periods

•The elements are arranged according to increasing atomic number (Z)

Group I – The Alkali Metals

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Group I – The Alkali Metals

•Good conductors of heat and electricity• Soft• Low density (float on water)•Dull quickly when cut• Low Melting points

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

Alkali Metal ReactionsGr I ReactionsBurn in oxygenLithium 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)

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)

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)

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.

Group II – The Alkaline Earth Metals •Harder than Gr I•Tarnish quickly•Less reactive than Gr I

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

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.

Group II•Like Gr I, they have characteristic flame colours (Table 3.9)

Group VII – The Halogens

Group VII – The Halogens•Halogen means “salt former” ie. NaCl•F, Cl, Br, I, At (radioactive)•Colours get darker going down the group

Group VII – The Halogens

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?

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.

Group VII – The HalogensReactions:•Halogens form acids with hydrogen Examples: HF, HCl, HBr, HI•They displace halogens below them (lab) Example Reaction:

2KBr + Cl2 2KCl + Br2

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

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

Group 0 – The Noble Gases

Neon Signs

The Transition Metals

•Much harder and denser than Groups I and II•High MP (except Hg)• Less reactive•Great catalysts (speed up reactions)

Hydrogen•A non-metal that can act as a metal•Usually grouped with Gr I or Gr VII