c) Group 7 elements - chlorine, bromine and iodine

c) Group 7 elements - chlorine, bromine and iodine 

2.8 recall the colours and physical states of the elements at room temperature. 

Group 7 Element	Colour	Physical state (at room temperature)
Chlorine	Green	Gas
Bromine	Red/brown	Liquid
Iodine	Dark grey	Solid

2.9 make predictions about the properties of other halogens in this group

As you travel down Group 7, the reactivity of the elements decreases. The elements will therefore have a darker colour and higher boiling point as you travel down the group, so fluorine will be the most reactive as it is the highest element in the group. It will have the darkest colour and the highest  boiling point. Then, the element furthest down in the group, Astatine, will have the lightest colour and the lowest  boiling point as it has the largest atomic number of all the elements in the group (the shell with the missing electron is furthest from the nucleus, so the pull from the positive nucleus is weaker.) 

2.10 understand the difference between hydrogen chloride gas and hydrochloric acid 

 Hydrogen chloride (HCI) is a gas at room temperature. Hydrochloric acid is hydrogen chloride dissolved in water. When dissolved in water, the HCI molecules split up into H+ ions and CI- ions in a process known as dissociation. The solution that is formed as a result of this is hydrochloric acid. Therefore, hydrogen chloride dissociates in water to form a solution of hydrochloric acid (it is an acid because it has H+ ions.) 

2.11 explain, in terms of disassociation, why hydrogen chloride is acidic in water but not in methyl benzene

Hydrogen chloride is acidic in water because it's molecules split into H+ and CI- ions in water, making it an acidic solution due to the presence of H+ ions. However, hydrogen chloride is not acidic in methyl benzene because it does not disassociate into H+ and CI- ions. With no H+ ions present, the hydrogen chloride is not an acid in methyl benzene. 

2.12 describe the relative reactivites of the elements in group 7

Group 7 elements become less reactive as you go down the group. The higher up Group 7 an element is, the closer the shell with the missing electron is to the nucleus, therefore the stronger the pull from the positive nucleus. The further down the element in Group 7, the further the electron shell with the missing electron and therefore the weaker the pull from the nucleus. 

2.13 describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts

A displacement reaction is one in which a more reactive element displaces a less reactive element from a compound. The elements in group 7 take part in these, following the rule that the elements are more reactive the higher up in the group they are. A more reactive halogen will displace a less reactive one that is bonded as a salt, but only if the salt is dissolved in water or a gas.

So for example chlorine is more reactive than iodine as it is higher up in Group 7. Therefore, if you add chlorine water to potassium iodide the more reactive chlorine will react with the potassium in the potassium chloride to displace the iodide, forming potassium chlorine. 

2.14 understand these displacement reactions as redox reactions

A redox reaction is a reaction in which both reduction (gain of electrons) and oxidation (loss of electrons) happens simultaneously. Displacement reactions between halogens and salt solutions are redox reactions because both oxidation and reduction occurs. 

So, in the reaction between chlorine water and potassium iodide, chlorine is reduced because it gains electrons and iodine is oxidised because it loses electrons. The displacement is therefore a redox reaction. 

2b) Group 1 elements - lithium, sodium and potassium

2b) Group 1 elements - lithium, sodium and potassium 

2.6 describe the reactions of these elements with water and understand that the reactions provide a basis for their recognition as a family of elements 

Group 1 elements (the alkali metals) all have one electron in their outer shell. As they are in the same group, they have similar chemical properties and will react with substances (including water) in a similar way. The Group 1 elements of lithium, sodium and potassium all react in a similar way with water, they react very vigorously which indicates that they are a family of elements and must have a similar electronic configuration. Although all the alkali metals will react similarly with water, as you go down Group 1 the elements become more reactive and will react more vigorously with water. 

Lithium: 

• Lump of lithium in water will move slowly around the surface, fizzing until it disappears. The water will become alkaline and the indicator solution will turn purple because of this. It will take approximately 30 seconds for this reaction to occur. Lithium is at the top of the group and is therefore the least reactive of all the alkali metals.

Lithium reacting with water. It will fizz like this until it disappears. 

Sodium; 

• The lump of sodium will fizz rapidly in the water and will move quickly around the surface.The indicator solution will turn purple as the water will become alkaline and it may even ignite. The time for this reaction to occur will be approximately 20 seconds. Sodium is further down in Group 1 than lithium, hence why it reacts more vigorously with the water and why it takes less time for this to happen. 

Sodium reacting with water. Having fizzed and moved quickly around the surface of the water,it has now ignited.

Potassium: 

• Lump of potassium will react vigorously with the water, and will burn with a lilac flame, or even explode. The indicator solution will again turn purple as the water has become alkaline. This reaction will occur in approximately 5 seconds. Potassium is the furthest down in Group 1 of all the three elements mentioned, hence why it reacts most vigorously with water and also why it has the quickest reaction time. 

                                                          

Potassium reacting with water. 

2.7 describe the relative reactivites of the elements in group 1

Elements in group 1 become more reactive as you go down the group. So, the least reactive metal in Group 1 is also the highest element in the group,so it would be lithium, then sodium, then potassium and so on. 

2.8 explain the relative reactivites of the elements in Group 1 in terms of distance between the outer electrons and the nucleus. 

The further you go down Group 1, the higher the period number of each element is. While the group number stays the same, the period number will increase. This means that as you go down the group, the elements have a higher period number, meaning they have more energy levels (shells.) Because of this, the elements' outer electrons will be further away from the nucleus as you go down the group, so the element will be able to lose electrons far easier as the attraction between the outermost and the nucleus becomes less. Therefore, the outer electron will be more easily lost and the element will be more reactive as you travel down Group 1.

2a) The Periodic Table

Section 2: Chemistry of the elements a) The Periodic Table 

2.1 understand the terms group and period 

Group = 

• The columns of the periodic table.
•  The number of the group an element is in tells you how many electrons it has in its outer shell (eg. If an electron is in group 3, it has 3 electrons in its outer shell.)
• Elements in the same group have similar chemical properties (same amount of electrons in their outer shell, they will therefore react and bond in similar ways)
• Properties of elements change as you go down a group. 

Period = 

• The rows of the periodic table. 
• The number of the period an element is in tells you how many energy levels (shells) it has. For example, if an element is in period 5 then it has 5 energy levels/ shells.
• Properties of elements change as you go along a period. 

2.2 recall the positions of metals and non-metals in the periodic table 

The elements on the left of the zig-zag are all metals. 

The elements on the right of the zig-zag are all non-metals.

2.3 explain the classification of elements as metals or non-metals on the basis of their electrical conductivity and the acid-base character of their oxides 

Metals: 

• Metals are good conductors of electricity because they allow charge to pass through them easily. (They have delocalised electrons which make it possible for an electrical current to pass through.) 
• Metal oxides are basic, and will therefore neutralise acids. Metal oxides which dissolve will form solutions with a pH higher than 7 (alkalis).

Non-metals 

• Non-metals are poor conductors of electricity because they are held tightly together by very strong covalent bonds, and are not free to move around or pass an electric current. 
• Non-metal oxides are acidic. They dissolve in water to form solutions with a pH of less than 7 (acidic.)

2.4 understand why elements in the same group of the Periodic Table have similar chemical properties 

Elements in the same group of the Periodic Table all have the same number of electrons in their outer shell. (Group number = number of electrons in outer shell.) Therefore, all of the elements in a group will have the same amount of electrons they need to gain/lose in order to become stable, meaning they will all react and bond with other elements very similarly and so have similar chemical properties. 

2.5  understand that the noble gases (Group 0) are a family of inert gases and explain their lack of reactivity in terms of their electronic configurations. 

All of the noble gases have full outer shells of electrons, so they are stable.  Because they are stable, they do not need to react with anything or form a bond, so they are also inert (unreactive). For example, helium is a noble gas that has 2 electrons in its outer shell (it only has one shell) , and is its therefore fully stable and inert.