Unit 1: Periodic Table

Unit 1: Periodic Table Part 1: Basic Structure of the Periodic Table

Underline the correct spelling. / Can you put the chemical symbol in this column? / Is the element a metal or non-metal?
Hydrogen / Hidrogen / Hydrogon
Lithium / Litheum / Lithiun
Sodum / Sodiume / Sodium
Potassium / Pottasium / Potasium
Silver / Sliver / Silvur
Guld / Geld / Gold
Kalcium / Calcum / Calcium
Oxegen / Oxigen / Oxygen
Sulphor / Sulpher / Sulphur
Magenesium / Magnesium / Magnecium
Carban / Carben / Carbon
Helium / Heelium / Hellium
Aluminium / Alumium / Aluminum
Copper / Coper / Coppur
Nickle / Nickil / Nickel

Starter Task

Periodic Table

The idea of the Periodic Table is to arrange the elements in a way that enables chemists to understand patterns in the properties of elements, but some reminders first.

An ATOM is the smallest particle of a substance which can have its own characteristic properties, BUT atoms are built up of even more fundamental sub-atomic particles - the electron, proton and neutron and the structure of an atom ultimately determines its properties.

An ELEMENT is a pure substance made up of only one type of atom, 92 of the elements in the Periodic Table (part of which is shown above) naturally occur, from hydrogen H (element 1) to uranium U (element 92).

Note that each element has symbol which is a single capital letter like H or U or a capital letter + small letter e.g. cobalt Co, chlorine Cl or sodium Na.

The majority of elements are readily divided into two types with common characteristic physical and chemical properties.

Most elements on the left are METALS e.g. elements 3 to 4 (lithium to beryllium), elements 11 to 13 (sodium to aluminium), elements 19 to 31 (potassium to gallium), elements 37 to 50 (rubidium to tin).

The elements on the right are NON-METALS e.g. elements 1 to 2 (hydrogen to helium), elements 5 to 10 (boron to neon), elements 15 to 18 (phosphorus to argon), elements 35 to 36 (bromine to krypton).

BUT a few elements are referred to as SEMI-METALS which have mixed metal/non-metal character and not so easy to classify, They occur in a diagonal band (down and L to R) e.g. silicon (14Si), germanium (32Ge), arsenic (33As) and tellurium (52Te).

The elements are laid out in order of Atomic (proton) Number

Many of the similarities and differences in the properties of elements can be explained by the electronic structure of the atoms (electron configuration = electron arrangement in shells or energy levels, so watch out the varying phrases used!).

The idea of the Periodic Table is to arrange the elements in a way that enables chemists to understand patterns in the properties of elements.

The main structural features of the periodic table are ...

to produce columns of similar elements called Groups.

They are usually similar chemically and physically BUT there are often important trends in physical properties and chemical reactivity up/down a group.

The resulting complete horizontal rows are called Periods and usually consist of a range of elements of different character.

There are important trends from left to right across a period e.g. the most important overall change is from metallic ==> non-metallic element character.

Certain 'horizontal blocks' of elements within a period, which have specific chemical features in common, may be known as a particular block or series e.g. from 21Sc to 30Zn are called the 1st Transition Metal Series within period 4.

The ideas of Group and Period are totally connected with electron structure

Task: Patterns in the Periodic Table

1) On the Periodic Table below, shade the metals in one colour and the non-metals in a different colour. Fill in the key to show which is which.

Key

2) On the Periodic Table below, shade the following in different colours: Group 1, Group 7, Group 0 and the transition metals. Fill in the key.

Key

3) On the Periodic Table below, write the atomic number of the first 36 elements in their boxes.

4) The first 20 elements in the Periodic Table are shown below (with the rest of the Table including the transition metals left out). Fill in the electronic structure of each element in the boxes.

Electronic Structure and the periodic table

Which of the elements Magnesium or Neon is the most stable?, give a reason for your answer.

......

What is the link between the position of the element in the periodic table and its electron configuration.

......

·  Most of the chemistry of an element is about what the outer electrons can do, or can't, as the case maybe.

·  and the atoms of other elements try to attain this sort of electron structure when reacting to become more stable.

Metals in the Periodic Table

Metals makeup more than 75% of the elements in the periodic table. Metals are characterized by the following physical properties.

1. They are ______.

2. They are usually ______at room temperature.

3. They are malleable. Malleable means that ______
______

4. They are ductile, this means that______

______

5. They are good conductors of ______and ______.

What is an alloy?

______

Explain why metals are often used in the form of alloys?.

______

References

IGCSE Chemistry pages 149-152

Learning Objectives

Candidates should be able to:

·  Describe the Periodic Table as a method of classifying elements and its use to predict properties of elements.

·  Describe the change from metallic to non-metallic character across a Period

·  Describe the relationship between Group number, number of valency electrons and metallic/non-metallic character.

Unit 1: Periodic Table Part 2: Alkali Metals (Group 1)

The alkali metals are in Group I of the Periodic Table. They

increase in reactivity as they increase in relative atomic mass.

Properties of Group 1 Metals. (Task- Fill in the gaps)

·  Good conductors of ______.

·  Good conductors of ______.

·  Very ______when first cut, although they ______quickly in air.

Unlike most everyday metals, they are

·  Very ______and can be easily cut with a knife.

·  Have ______densities and can ______on water.

·  Have relatively ______melting and boiling points.

Burning Group I metals in Air.

Group I metals are so reactive they have to be stored in oil to stop them from reacting with air or water.

Group I metals react with oxygen in the air to form the metal oxide. The oxide of a metal is a powdery compound.

metal + oxygen à metal oxide

When lithium burns in air you see a bright red flame.

lithium + oxygen à lithium oxide

4Li (s) + O2 (g) à 2Li2O (s)

Flame tests

It's possible to test a compound to detect the presence of an alkali metal ion.

A cleaned, moistened flame test wire is dipped into a solid sample of the compound and then put into a blue Bunsen flame. The flame colour indicates which alkali metal ion is present in the compound.

Flame colours and the alkali metal ion they represent

Flame colour / Ion present /
red / lithium
orange / sodium
lilac / potassium

Reactions with Water.

Group I metals react with water to form metal hydroxides. Hydrogen gas is given off in this reaction.

Sodium + water à sodium hydroxide + hydrogen

2Na(s) + 2H2O(l) à 2NaOH (aq) + H2(g)

Sodium hydroxide dissolves in water and the solution is a strong alkali. All Group I metals form alkalis in water, which is why they are called Alkali Metals.

Task

1) Complete the table below (parts have been done for you already).

Element Symbol / Atomic
number / Density
(g/cm3) / Melting point (ºC) / Boiling
point (ºC) / State at
25ºC / State at
100ºC
Lithium / 0.53 / 181 / 1342
Sodium / 0.97 / 98 / 883
Potassium / 0.86 / 63 / 780 / Liquid
Rubidium / 1.53 / 39 / 684
Caesium / 1.88 / 29 / 669 / Solid

2) Water has a density of 1g/cm3. If an object has a density greater than this, it will sink.

a)  Which group 1 elements will float on water, and which will sink?

b)  What can you say, in general, about the densities of the group 1 metals?

3) Underline the correct words in each bold pair or trio in the following sentences:

Lithium, sodium and potassium are very easy / difficult to cut with a scalpel. Lithium / potassium sets on fire easily when it reacts with water. When these metals react with water, they make a gas called oxygen / hydrogen / carbon dioxide. We test for this gas using a lighted / glowing splint which relights / pops. At the end of experiment, the universal indicator in the water is red / green / purple. When these metals react with water, they make acidic / alkaline / neutral solutions.

4) When lithium reacts with water, it makes lithium hydroxide and hydrogen.

The word equation for this reaction is:

lithium + water à lithium hydroxide + hydrogen

a) Sodium reacts with water in a similar way. Complete the word equation:

sodium + ______à sodium hydroxide + ______

b) Potassium also reacts with water in a similar way. Write the word and symbol equation:

______

5) Plot a graph of melting point (vertical axis) against atomic number (horizontal axis). Describe your graph in a much detail as you can – what does it show you about how the melting points of the group 1 metals change as the atomic number increases?

References

IGCSE Chemistry pages 149-152

Learning Objectives

Candidates should be able to:

•  Describe the properties and reactivity of lithium, sodium and potassium in Group 1

•  Use the trends within the group to predict the properties of other elements.

Unit 1: Periodic Table Part 3: Reactivity Series

How metals react with oxygen

Metals react with the oxygen in air, forming oxides. This can often be made clearer by reacting the metal with pure oxygen.

magnesium + oxygen → magnesium oxide

Here magnesium metal has reacted with the oxygen in the air and has been oxidised. This means that oxygen has joined to the magnesium making a compound from the elements. The compound is called magnesium oxide.

In general: metal + oxygen + metal oxide.

zinc + oxygen → zinc oxide

copper + oxygen → copper oxide

calcium + oxygen → calcium oxide

There are a few metals that do not react with oxygen in the air. They include the very unreactive metals gold, platinum and silver.

How metals react with water

Metals above hydrogen in the reactivity series will react with water. The metals below hydrogen - like copper, silver and gold - do not react with water or steam.

Lithium, sodium, and potassium all react well (fast, vigorously) with cold water. These metals react and dissolve, producing an alkaline solution - a metal hydroxide solution which turns Universal Indicator purple. While reacting, hydrogen (which is a flammable gas) is given off, making a fizzing noise.

lithium + water→ lithium hydroxide + hydrogen

potassium + water→ potassium hydroxide + hydrogen

sodium + water→ sodium hydroxide + hydrogen

Magnesium is less reactive than these three. Therefore it only reacts slowly with cold water. It will react vigorously with steam. The products are slightly different as the oxide is formed.

Once the magnesium has become very hot it starts to react with the steamin a very exothermic reaction. The magnesium, which was silver in colour, becomes pure white and a flammable gas - hydrogen - is formed. This is set on fire. The word equation is:

magnesium + water (steam) → magnesium oxide + hydrogen

How metals react with acids

Metals above hydrogen in the reactivity series react with dilute acids. The reaction involves the metal dissolving and fizzing as hydrogen gas is formed.

The test tube gets warm because the reaction produces thermal energy - i.e. it is exothermic.

The general word equation is: acid + metal → hydrogen gas + a salt

A salt is a compound made from an acid when a metal has replaced the hydrogen. The table below gives you the names of the salts formed when using each acid.

Below are some examples of reaction between metals and acids:

zinc + sulphuric acid → zinc sulphate + hydrogen

nitric acid + magnesium → magnesium nitrate + hydrogen

calcium + hydrochloric acid → calcium chloride + hydrogen

The chemical test for hydrogen gas:

Take a lighted splint or spill and place it in the gas. If there is a squeaky pop - and often the splint or spill is blown out - then the gas is hydrogen.

Reactivity of Metals- Summarized

Displacement reactions

A displacement reaction happens between a reactive metal and a solution of a less reactive metal compound. The more reactive metal will displace the less reactive metal from its compound in solution.

Here's what you observe (see, hear, feel) in this type of reaction:

The more reactive metal will dissolve.

The less reactive metal will appear at the bottom of the tube or plate on the more reactive metal.

The solution may change colour.

These reactions are exothermic, so the tube gets warm.

Examples of displacement reactions

copper sulphate solution + magnesium → magnesium sulphate solution + copper

iron + copper sulphate solution→ iron sulphate solution + copper