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AS Chemistry (Unit 1: F321) > The periodic table > Flashcards

Flashcards in The periodic table Deck (20)
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1

How are the elements arranged in the modern periodic table?

In order of increasing atomic number.

2

What is a period and how do elements in a period relate to each other?

- A horizontal row in the periodic table.- Elements in the same period have different electron configurations and different orbitals but the outer electrons are in the same quantum shell.- Elements in the same period show a trend in physical and chemical properties.- This trend is called periodicity.

3

What is a group and how do elements in a group relate to each other?

- A vertical column down the periodic table.- Element in the same group have the same number of electrons in the outer shell and the same orbitals but on different quantum shells.- Elements in the same group show similar physical and chemical properties since they have similar electron configurations.

4

What is the trend in atomic structure across a period?

Across a period, first ionisation energies increase. This is because the nuclear charge is increasing, so the force of attraction from the nucleus on the electrons is also increasing. However, the additional electrons are also going into the same quantum shell so they experience the same amount of electron shielding. Distance actually decreases as the atomic radii decreases across a period which further increases force of attraction between nucleus and electron. All this means that the effective nuclear charge increases across a period so first ionisation energies also increase.Also as a result of the increase in effective nuclear charge, the electrons get pulled more and more inwards across a period so atomic radii decreases across a period.

5

What is the trend in atomic structure down a group?

Down a group, first ionisation energies decrease despite the increases in nuclear charge. This is because as you go down a group, the atoms of elements are increasing in size by one quantum shell each time. This means that the outer electrons of each atom is experiencing one more shell worth of electron shielding as well as well as an increase in distance from the nucleus. All this counteracts the increased nuclear charge and thus first ionisation energies decrease. Atomic radii also increases down a group as a result of the increased shielding. this means that the electrons do not experience as strong an effective nuclear charge and are not pulled in as closely as each other. This results in the atomic radii increasing down a group.

6

What are the trends in reactivity for group 2 metals?

As you go down the group, the metals become more reactive. This is because group 2 metals usually undergo oxidation to form 2+ ions. As you go down the group:
1. Atomic radii increases.
2. Electron shielding increases.
3. 1st and 2nd ionisation energies decrease.
All this means that as you go down the group, the metal atoms can more easily lose (with less energy) their 2 outer shell electrons and react to form 2+ ions.

7

What is the trend in solubility of group 2 hydroxides?

Hydroxides become more soluble as you go down the group and the solutions formed increase slightly in pH. However, the typical pH of any group 2 hydroxide solution is 10-12.

8

What is the trend in thermal decomposition of group 2 carbonates?

Group 2 carbonates decompose more easily as you move up the group. I.e. as you move down the group, higher temperatures are required to decompose the carbonate.

9

What is the common name for calcium carbonate?

Limestone.

10

What is the common name for calcium oxide?

Quicklime.

11

What is the common name for calcium hydroxide?

Slaked lime.

12

What is the use of calcium hydroxide?

To neutralise acidic soil.

13

What is the use of magnesium hydroxide?

Used in 'milk of magnesia' to neutralise stomach acid in indigestion.

14

What is the trend in boiling points down group 7?

Boiling points increase as you go down the group because as you go down the group, there are ore electrons in each halogen atom and therefore there are more electrons in each halogen molecule. As there are more electrons in each halogen molecule, there are stronger fluctuations in the electron cloud; resulting in stronger instantaneous and stronger induced dipoles. This results in stronger van der waals interactions between molecules and more heat energy is required to break them.

15

What is the trend in reactivity down group 7?

Reactivity decreases as you go down the group. This is because halide atoms usually undergo reduction to form 1- ions. As you go down the group:
1. Atomic radii increases.
2. Electron shielding increases.
All this means that electrons on the outer shell experience a smaller effective nuclear charge, so as you go down the group, the halogen atoms are less able to hold onto electrons gained during reaction; resulting in decreasing reactivities.

16

How is the reactivity of halogens determined?

A halogen solution is usually added to an aqueous halide salt. If the halogen added is more reactive than the aqueous halide ion, a displacement reaction occurs where the halide is displaced to form a halogen. Halogen solutions are coloured and a colour change can be observed:
- Chlorine is pale-green coloured.
- Bromine is orange coloured.
- iodine is brown coloured.
A further test can be carried out to distinguish between vague colours. Cyclohexane is added to the mixture and the mixture is shaken.
- If the cyclohexane doesn't change colour, chlorine is present.
- If the cyclohexane turns orange, bromine is present.
If the cyclohexane turns purple, iodine is present.

17

What is a displacement reaction?

A reaction in which a more reactive element displaces a less reactive element to form an aqueous solution of the latter's ions.

18

What is a disproportionation reaction?

A redox reaction where an element is both oxidised and reduced.

19

What are the uses of chlorine?

1. Chlorine reacts with water to form HClO (bleach). This ion is able to destroy bacterial membranes and kill bacteria. Chlorine is therefore added to swimming pools and drinking water as an antibacterial agent.
2. Chlorine reacts with NaOH to form NaClO which is the primary ingredient used in commercial bleach.

20

What is the potential danger of chlorinating drinking water?

Some believe that chlorine can react with organic compounds in the body to form chlorinated hydrocarbons. These chlorinated hydrocarbons are said to be carcinogenic.