3.1 - Development of Periodic table

Question 1

What did John Newlands do?

Answer 1

He created the ‘Law of Octaves’ - elements showing similar properties to other elements that were eight spots ahead in his version of the periodic table.

Question 2

What did Dmitri Mendeleev do?

Answer 2

Created the modern periodic table - ordered elements with similar properties in vertical columns, with gaps left for elements that would be discovered in the future.

Question 3

How are the elements organised in Mendeleev’s table?

Answer 3

In order of atomic mass, with elements that share similar properties in vetical columns.

Question 4

What did Henry Mosely do?

Answer 4

• Modified Mendeleev’s periodic table to place elements based on atomic numbers, rather than atomic mass.
• Determined atomic number for all known elements.

Question 5

In the modern periodic table, what are groups and what are periods?

Answer 5

• Groups are vertical columns of elements that have similar properties.
• Periods are horiontal rows of elements, with atomic number increasing from left to right.

Question 6

Which side of the periodic table is S block?

Answer 6

The far left side

Question 7

Which side of the periodic table is D block?

Answer 7

the centre

Question 8

Which side of the periodic table is P block?

Answer 8

The far right side

Question 9

What are the three factors that electron attraction depends on?

Answer 9

• Atomic radius
• Nuclear charge
• Electron shielding

Question 10

What is atomic radius?

Answer 10

The width of the atom - the larger the atomic radius, the less attraction the outer electrons experience due to decreased proximity with the nucleus.

Question 11

What is Nuclear charge?

Answer 11

The number of protons in the nucleus - the higher the nuclear charge, the larger the attractive force is on the outer electrons.

Question 12

What is electron shielding?

Answer 12

Inner shells of electrons repelling outer shells of electrons - The more inner shells there are, the larger the shielding effect is and the less attraction is felt on the outer electrons.

Question 13

What is the trend in successive ionisation energies?

Answer 13

Each successive ionisation energy is higher than the one previous to it.

Question 14

Why is there a trend in successive ionisation energies?

Answer 14

The positive nuclear charge outweighs the negative charge incrementally every time an electron is removed, making the atomic radius smaller, which means that more energy is required to further ionise the atom/ion.

Question 15

What group of elements has the highest first ionisation energies?

Answer 15

• Noble gases - Helium, Neon, Argon, Xenon, etc.

- Full outer shell of electrons - high positive attraction from nucleus.

Question 16

Why does ionisation energy increase across a period?

Answer 16

• Number of protons increases - higher nuclear charge.

- Same number of inner shells, so electron shielding does not increase to lower the ionisation energy.

Question 17

What is the definition of a metallic bonding?

Answer 17

Positive metal cations occupy fixed positions in a lattice in a sea of delocalized electrons.

Question 18

What are the properties of giant metallic lattices?

Answer 18

• good conductors
• high melting + boiling points
• ductile
• malleable

Question 19

What is the trend in melting and boiling points of metallic substances across period 2?

Answer 19

Melting + Boiling points increase due to extra electrons and greater nuclear charge.

Question 20

What are the physical properties of group 2 elements?

Answer 20

• reasonably high melting / boiling points
• light metals w/ low densities
• form colourless (white) compounds

Question 21

Why do group 2 elements react so vigorously with oxygen?

Answer 21

They can donate their two outer electrons to the two empty spaces in the oxygen atom’s full outer shell.

Question 22

What is a redox reaction?

Answer 22

A reaction where a substance is oxidised (oxidation number increases) and a substance is reduced (oxidation number decreases)

Question 23

When groups 2 oxides react with water, they form…

Answer 23

metal hydroxides (pH 10-12)

Question 24

What is the trend in solubility of group 2 hydroxides?

Answer 24

• The solubility increases down the group, as does the alkalinity.
• Be, at the top of group 2, is insoluble in water.

Question 25

What is the trend in boiling point of the halogens? (group 7)

Answer 25

Boiling point increases down the group.

Question 26

What is disproportionation in a redox reaction?

Answer 26

When the same element is both reduced and oxidised

- e.g. Cl2 oxidation number going from 0 to +1 in HCLO, but also going from 0 to -1 in HCl.

Question 27

How do you test for Carbonate anions? (CO3 2-)

Answer 27

reacts with acids to form effervescence and carbon dioxide.

Question 28

How do you test for Sulfate anions? (SO4 2-)

Answer 28

Reacts with barium ions to form a white precipitate of Barium Sulfate

Question 29

How do you test for Chloride ions?

Answer 29

• Silver nitrate - turns solutions white

- soluble in dilute NH3

Question 30

How do you test for Bromide ions?

Answer 30

• Silver nitrate - turns solution cream

- soluble only in concentrated NH3

Question 31

How do you test for Iodide ions?

Answer 31

• Silver nitrate - turns solution yellow

- insoluble in NH3