3A - The Periodic Table

Question 1

Trends across a period? (5)

Answer 1

• Nuclear charge increases
• Same shell, similar electron shielding
• Nuclear attraction increases
• Atomic radium increases
• 1st ionisation energy increases

Question 2

Trends in first ionisation energy down a group? (4)

Answer 2

Decreases as you go down a group.

• Atomic radium increases
• More inner shells so sheilding increases
• Nuclear attraction on outer electrons decrease
• First ionisation energy decreases

Question 3

How are elements in the periodic table arranged?

Answer 3

Elements in the periodic table are arraged in order of increasing atomic number

Question 4

Proterties of elements in the same period? (3)

What do elements in the same period show? Why?

Answer 4

• Different number of electrons in the outer shell
• Different types of orbitals in the outer shell
• Outer electrons are in the same quantum shell

Elements in a period show a trend in physical and chemical properties because they have different electronic configurations.

Question 5

Proterties of elements in the same group? (3)

What do elements in the same group show? Why?

Answer 5

• Same number of electrons in the outer shell
• Same types of orbitals in the outer shell
• Outer electrons in different quantum shells

Elements in the same group show similar physical and chemical properties because they have similar electronic configurations.

Question 6

What is periodicity?

Answer 6

It’s the regular pattern in properties of the elements across different periods

Question 7

How is a subshell different to a oribital?

Answer 7

Subshell = collection of orbitals

Orbital = Only contains up to 2 electrons

Question 8

Define first ionisation energy

Answer 8

The amount of energy required to remove one mole of electrons from one mole of a gaseous atoms to form one mole of gaseous ions

Question 9

Equation for first ionisation:

1. Boron
2. Nitrogen
3. General equation (X)

Answer 9

1. B_(g) → B^-_(g) + e^-
2. N_(g) → N^3- + e^-
3. X_(g) → X^- + e^-

Question 10

Indicate where the elements of period 1, 2 and 3 start

Answer 10

Question 11

Describe the general trend in first ionisation energy change across a period

Answer 11

Increases as you go across the period

Question 12

How does the first ionisation change down a group?

Answer 12

Decreases because the number of protons in the element increase. This increases the nuclear charge of the element.

Question 13

Why do the first ionisation energies drop sharply between the group 0 element of one period and to the group 1 element of the next period?

Answer 13

You have to take out the electron from another energy level, there’s more sheilding electrons.

Question 14

4 factors that affect the value of ionisation energies?

Answer 14

Charge of nucleus

Sheilding electrons

Distance from nucleus

Nuclear attraction - A consequence of the other 3 factors

Question 15

Explain the atomic structure for general trends in first ionisation energy:

1. Across a period
2. Down a group

Answer 15

1. As you move across the period, first ionisation energy increases.

Nuclear charge increases.

Sheilding electrons and distance from nucleus stays the same.

2. As you go down a group, first ionisation energy decreases.

Less nuclear attraction.

Distance from nucleus and sheilding electrons increase (this becomes the more important factor)

Question 16

Group 2 metals reactions with:

Oxygen

Water

Dilute acids

Answer 16

Metal + Oxygen → Metal oxide

2M_(s) + O_2(g) → 2MO_(s)

Metal + Water → Metal hydroxide + Hydrogen

M_(s) + 2H₂O_(l) → M(OH)_2(aq) + H_2(g)

Metal + Acid → Salt + Water

Question 17

Group 2 Metal oxide + Water → ?

pH of solution formed when group 2 Metal oxide + water?

Answer 17

Metal oxide + water → Metal hydroxide

Solutions formed are metal hydroxides which are alkaline

pH = approx 10-12

Question 18

List 3 different types of periodicity between period 2 and 3

Answer 18

Melting point and boiling point

Electrical conductivity

Atomic radius

Question 19

7 rules when assigning oxidation numbers

Answer 19

1. Uncombined elements = 0
2. Elements in simple ions has the same oxidaiton number as the charge on the ion e.g. I^- = -1
3. Fluorine = -1
4. Oxygen = -2 (except in a peroxide then it’s -1)
5. Hydrogen = +1 (except in hydride then it’s -1)
6. Group 1 metal = +1
7. Group 2 metal = +2

Question 20

Reactivity trends of group 1 and group 2 metals?

Answer 20

Group 1 metals = More reactive as you go down the group.

Group 2 metals = More reactive as you go up the group.

Question 21

Give the 1st and 2nd ionisation energy equation of calcium

Answer 21

1st: Ca_(g) → Ca⁺_(g) + e^-
2nd: Ca⁺_(g) → Ca²⁺_(g) + e^-

Question 22

Describe the trend in solubility of the group 2 metal hydroxides as you move down the group

Answer 22

Solubility increases as you go down the group. The strength of the electrostatic force of attraction between the OH^- ions and the metal ions decrease as you go down the group

Question 23

How is the solubility of the metal hydroxides related to their alkalinity?

Answer 23

As solubility increases the alkalinity increases.

If the metal hydroxide is more alkaline it’s more likely to relase the OH^- ions.

Question 24

For Chlorine, bromine and iodine:

• State at RTP
• Appearance at RTP
• Associated hazards

Answer 24

Chlorine:

• Gas
• Green gas
• Poisonous by inhalation as it forms HCl in lungs

Bromine:

• Liquid
• Brown liquid (with orange vapour)
• Toxic, corrosive.

Iodine:

• Solid
• Grey
• Toxic vapour when heated

Question 25

What type of attraction exist between halogen molecules?

Answer 25

London forces - Caused by the fluctuations in the distribution of electrons which will cause an instantaneous dipole.

They can’t have a permanent dipole as the 2 molecules are similar in electronegativity.

Question 26

What colour is Cl₂,Br₂ and I₂ in water and in hexane?

What about Cl^-,Br^- and I^-?

Answer 26

Question 27

When an organic solvent such as hexane is added to a solution containing halogens 2 layers form.

Explain, with reference to intermolecular forces, why 2 layers form.

Answer 27

The hexane is non-polar, it only forms London forces between molecules.

Water is polar and forms hydrogen bonds between molecules.

The layers are immiscible (do not mix) as a polar substance won’t dissolve a non-polar substance.

Question 28

When an organic solvent such as hexane is added to a solution containing halogens 2 layers form.

Explain why adding the organic solvent is necessary to allow proper identification of the halogens in solution.

Answer 28

They’ll all look the same in water alone.

Halogens are held together by london forces. They’re favour in dossolving into the hexane than the polar solution of water.

This means that only the hexane will have a colour change.

Question 29

Define disproportionation

Answer 29

The reaction in which the same element is both oxidised and reduced

Question 30

Chlorine + water → ?

Chlorine + cold, dilute NaOH → ?

Answer 30

Chlorine + Water → Chloric (I) acid + Hydroden chloride

Cl_2(g) + H₂O_(l) → HClO_(aq) + HCl_(aq)

Chlorine + cold, dilute NaOH → Sodium chlorate (I) + Sodium hydroxide + Water

Cl_2(g) + 2NaOH_(aq) → NaClO_(aq) + NaCl_(aq) + H₂O_(l)

Question 31

Use of Sodium chlorate (I) - NaClO?

Answer 31

Household bleach

Question 32

Suggest why sodium chlorate (I) is more effective as a bleach than chloric (I) acid?

Answer 32

Sodium clorate (I) fully dissociates where as chloric (I) acid only partially dissociates