Chemistry - periodic table P2

Periodic table:

• It arranges the elements in order of atomic number

• elements with similar properties line up in vertical columns (called groups)

• Horizontal rows across the periodic table is called periods

• Most elements are solids (state) at room temperature

• The only elements that are in liquid temperatures Mercury and Bromine

• There is an imaginary diagonal stepped line that divides the metals from non-metals

What are metals/ non metals like?

• Metals are good conductors of heat and electricity

• Metals are shiny (when polished) malleable (can be hammered into shapes) and ductile (can be drawn out into wires)

• Most metals are hard, dense, and have high melting points

• Iron, Cobalt, Nickle are the magnetic metals

• Non metals are poor conductors of heat and electricity

• Non metals are usually soft and brittle

• Most non - metals have low melting / boiling points so many are gases (state room temperature)

• Metal oxide are alkaline non-metal oxides are acidic

How does the periodic table organise the elements?

periodic table organise elements by atomic number, chemical properties and electronic structure

What did scientists observe about about chemicals?

They observed that the chemicals have a difference in reactivity

Which gases are completely unreactive with everything?

Noble gases (group 8)

Give an example of a metal which has a vigorous reaction with water. Which group is it in?

Potassium, Sodium and Lithium (Group 1)

Why were elements ordered by atomic mass?

Protons weren’t discovered yet

In which year did Mendeleev form the first table of elements? And why was it accepted by the scientific community?

• 1867

• He correctly predicted the properties of gallium

What was the mystery element with atomic number 68 which was discovered in 1867?

Gallium

Why was this a turning point in the world of chemistry?

It allowed you to predict properties of unknown elements

What were the remaining problems?

Noble gases weren’t discovered and the ordering of atomic weight

Electronic structure

• Elements in group 1 have 1 electron in their outer shell, in group 2 they have 2 electron in their outer shell and so on.

• Elements in the same group of the periodic table react in a similar way because their atoms have the same number of electrons in the highest occupied energy level

why do elements react?

Because of their electronic structure

what does periodic mean in the term periodic table?

• There is an order of strings repeating

• (properties of elements repeat in a regular pattern when they are arranged in order of increasing atomic number)

what is a group what is a period

• vertical groups

• horizontal periods

How do the electronic structures of the atoms of a metallic element change when they react?

When metallic elements react they lose 1 or more electrons form their outer shell to form positive ions

Explain why the noble gases are so unreactive (group 8)

They already have full outer electron shells

Experiment 1 - appearance

Which group has the shiny appearance?

Metals - silver - shiny, copper - bronze, Magnesium - shiny

Which group has a dull appearance?

Non - metals - Hydrogen, oxygen, chlorine - clear sulfur, carbon - yellow

Experiment 2 - conduction of heat

This is strips of different metals: brass copper iron and aluminium dipped into hot water and must state which one heats the quickest in order

Copper, Aluminium, Brass, Steel

Experiment 3 - Conduction of electricity

Simple electrical circuit. Make sure bulb lights up

which ones conduct electricity?

copper zinc steel

which ones don’t conduct electricity?

straw wood

Experiment 4 - Sound

Use a small hammer and ht the 2 materials (cans)

Which ones are sonorous?

metals are sonorous

Experiment - Malleable or brittle

Provided some metals and non metals

which ones can you bend the material without breaking?

Copper, Tin, Zinc, Straw - malleable

Wood, Pasta - Brittle

Experiment 6 - Density

density = mass / volume

based in the different blocks work out the mass and volume and divide them to get the density

Experiment 7 - Melting points

Do metals or non metals have the higher melting and boiling points?

Metals generally have significantly higher melting and boiling points than non - metals

Alkali metals

element colour hard? does it tarnish? Electrical conductivity m.p. b.p. density

lithium no/ silver no yes yes 181 1347 0.53

sodium no/ silver no yes yes 98 883 0.97

potassium no/ silver no yes yes 64 774 0.86

rubidium no/ silver no yes yes 39 686 1.53

caesium no/ silver no yes yes 28 671 1.87

What colour are alkali metals?

Silver

Are alkali metals hard or soft?

soft

what happens as you descend the group ?

As you descend the group the melting / boiling points of the metals decrease

What are the densities of alkali metals like?

The alkali densities of lithium sodium and potassium are all below one, therefore they float on water

Reaction of alkali metals

As you go down the group in the periodic table the number of complete energy shells increases. This means the atoms become larger. In group 1 the atoms want to lose an electron when they react. Larger atoms lose electrons more easily than smaller ones because

• outermost electron further from nucleus

• inner shells of electron shields the outermost electron from nuclear charge

• greater nuclear charge of larger atoms have less electrostatic attraction towards outer most electron due to the size and shielding

words / symbols

• words: caesium + water → caesium hydroxide + hydrogen

• symbols: 2Cs + 2H2O → 2CsOH + H2

• words: rubidium + oxygen → rubidium oxide

• symbols: 4Rb + O2 → 2Rb2O

• words: sodium + chlorine → sodium chloride

• 2Na + Cl2 → 2NaCl

Forming Sodium Ion

There is an electrostatic attraction between:

the positively charged nucleus (protons)

and the negatively charged electrons.

When sodium reacts, it loses its outermost electron.

The outer electron gains enough energy to leave the atom.

Electrons that are further from the nucleus are easier to remove.

Inner electron shells protect (shield) the outer electron from the nucleus’ pull.

After losing one electron, sodium becomes a sodium ion (Na⁺) with electron arrangement 2,8.

Properties of alkali metals

lithium - deep red flame

sodium - deep yellow flame

potassium - lilac flame

rubidium - catches fire as soon as exposed to air and burns fiercly

caesium - melts in warm room can explode on exposure to air

Halogens/ why do they become less reactive as you go down the group?

Become less reactive as you go down the group - As its easier to gain electrons because numbers are positive and with less shells they are closer making it easier to attract. Atomic radius increases or more energy levels / shells. Attraction between nucleus and outer electron reduces due to inc. in shielding.

Table:

halogens

Fluorine

chlorine

bromine

Iodine

What do diatomic molecules mean? And name the 7 diatomic molecules

• they travel in 2 pairs

• Hydrogen, oxygen fluorine nitrogen bromine chloride iodine

• (H,O,F,Br,I,N,Cl)

Experiment (REACTIONS) - S = Solution W = Water

• Chlroine S + Potassium Chlorine S = X

• Bromine W + Potassium Chlorine S = X

• Iodine S + Potassium Chlorine S = X

• Chlorine S + Potassium Bromide S = Brown/ orange soln

• Bromine W + Potassium Bromide S = X

• Iodine S + Potassium Bromide S = X

• Chlorine S + Potassium Iodine S = Brown/ orange soln

• Bromine W + Potassium Iodine S = Brown/ orange soln

• Iodine S + Potassium Iodine S = X

words / symbols

• Potassium Iodine + Chlorine (gas)→ Potassium chloride + iodine

• 2Kl + Cl2 → 2KCl + I2

• Potassium iodine + Bromine → Potassium bromide + iodine

• 2KI + Br2 → 2KBr + I2

• Potassium bromide + Chlorine → Potassium chloride + Bromine

• 2KBr + Cl2 → 2KCl + Br2

Uses of noble gases

• Helium - It is used for balloons and airships used for medical applications like MRI, respiratory therapy

• Neon - Signage and lighting, lasers, electrical equipment

• Argon - welding, manufacturing industry

• Krypton - Fluoride lasers,- for medical issues, Insulation and other applications, energy efficient windows