• The Periodic table is a method of classifying elements.
• Elements are arranged in order of increasing atomic number (each proceeding element has one more proton)
• Made up of rows called periods and columns called groups; the position of an element helps determine its electronic configuration
• Period number: number of electron shells
• Group number: number of valency electrons (outer shell electrons)
• Elements in the same group have similar chemical properties.

 

Periodic Trends

1. Table moves from metals on the left to non-metals on the right.
2. Down a group of metals, elements become more reactive
3. With non-metals, going down a group, reactivity decreases

 

Alkali Metals

• Group I metals: Lithium, sodium and potassium

 

Chemical Properties	Physical Properties
Readily react with oxygen and water; stored in oil	Good conductors of heat and electricity
React violently with chlorine	Soft and easy to cut
Burst into flames when heated with oxygen[red flame for lithium; yellow flame for sodium; lilac flame for potassium]	Shiny when freshly cut
Produce soluble white compounds.	Low melting and boiling points compared to most metals.
React with water to form alkaline metal and hydrogen gas	Low densities for metals

Group II

They are alkali earth metals as they are commonly found naturally in minerals. They have two electrons in the valency shell

Physical properties

They are good conductors of heat and electricity. They have low Melting and boiling points which increases down the group. They also have low density which also increases down the group.

Trends in their chemical properties

Reactivity increases down the group as the atoms increases. They are less reactive than group 1 as they lose two electrons

• Their reaction with oxygen
• All group 2 metals reacts in air forming oxides (white)
• eg CaO, MgO, BaO(s)…
• Their reaction with water

• they make ionic compounds of +2 charge.
• they react with water to form metal oxides eg Mg(OH)₂, Ca(OH)₂..
• Mg reacts very slowly with cold water but readily with steam

 

Group VII : The halogens

A non-metal group eg florine (pale yellow), chlorine (greenish yellow), bromine (reddish brown) and iodine (shiny black). Form colored gases. Do not conduct electricity. Form diat omic molecules (means they exist as 2 atoms) eg Cl₂. Elements become darker and solidify down the group. All halogens are poisonous.

Trends in their physical properties of VII

• size and mass of atom increases
• density also increases
• melting and boiling points also increase

Trends in their chemical properties of VII

• reactivity increases down the group.
• the smaller the atom (only one electron short of a afull shell), the easier it is to attract the electron hence reactivity increases

 

Uses of VII elements (halogens

As bleaching agents eg chlorine (to bleach wood pulp in paper-making industry). Water purification as chlorine kills bacteria in water.

 

Properties	Patterns
States and Colors, at RTP: Fluorine- Yellow gas Chlorine- Green gas Bromine- Red liquid Iodine- Black solid	Down the group; size, mass and density increase
Poisonous	Down the group, color darkens
Diatomic; form halide ions in displacement reaction	Reactivity decreases down the group, because it has to gain an electron, so the closer the electron is to the positive nucleus the more easily it will be gained, so atoms with fewer shells will react more easily.
Do not conduct electricity	melting point increases down the group
Brittle and crumbly when solid

 

Transition Metals

• High melting points (except mercury)
• Malleable and ductile
• Good conductors of heat & electricity (silver is the best)
• High density
• Have no trend in reactivity
• Used as catalysts
• Form colored compounds
• Can form complex ions as they have variable valences

 

Noble Gases

Properties	Uses
Density increases down the group	Helium- filling balloons and aircrafts because it is lighter than air and will not catch fire.
Monoatomic and colorless	Argon – filling (tungsten) light bulbs to stop the filament reacting with oxygen.
M.P. and B.P. increases down the group	Neon – is used in advertising signs because it glows red.
Don’t conduct electricity
Inert due to full outer shell electrons

 

Metals and non-metals

• from left to right, elements gradually change from metal to non-metals
• metals are on the left side of the periodic table.
• non-metals are found on the right side of periodic table.
• metalloids show properties of both metals and non-metals