2.1 Periodicy

Question 1

How are the elements in the periodic table arranged ?

Answer 1

By their proton number.

Question 2

What is a period on the periodic table ?

Answer 2

The horizontal rows.

Question 3

What is a group on the periodic table ?

Answer 3

The vertical columns.

Question 4

What does the group number represent on the periodic table ?

Answer 4

The outer electrons of an elements .

Question 5

What are the 4 blocks of the periodic table ?

Answer 5

•s block (group 1 and 2)
•p block (group 3 to 8)
•d block (transition metals)
•f block (bottom rows)

Question 6

What is periodicy ?

Answer 6

The study of trends within the periodic table, often these are linked with electron configuration.

Question 7

What is the trend in atomic radius across a period ?

Answer 7

Atomic radius decreases across a period.

Question 8

Why does atomic radius decrease across a period ?

Answer 8

•The protein number increases across a period, meaning there is a greater attraction between the nucleus and outer electrons
•Because there is the same number of shielding electrons in a period, this results in the outer electrons being pulled closer to the nucleus.

Question 9

What is the trend in atomic radius going down a group ?

Answer 9

It increases.

Question 10

Why does atomic radius increase going down a group ?

Answer 10

•As you go down a group, more electrons are added to each element
•These electrons are organised into orbitals which come at increasingly large distances from the nucleus due to electrons negative repulsion
•The additional protons in the nucleus have no substantial effect as there are additional shielding electrons present in each step down a group.

Question 11

What is the trend in ionisation energy across a period ?

Answer 11

Along a period, first ionisation energy increases.

Question 12

Why does ionisation energy increase across a period ?

Answer 12

•It increases as atomic radius decreases, hence nuclear charge increases
•This means that each electron requires more energy to displace.

Question 13

What is the trend in ionisation energy going down a group ?

Answer 13

It decreases.

Question 14

Why does the ionisation energy decrease down a group ?

Answer 14

•The atomic radius of elements increases down a group, which means the attractive force is weaker for the outermost electrons as you progress down a group
•This means less energy is required to displace electrons further down a group.

Question 15

What does the melting point of period 3 elements depend on ?

Answer 15

•The structure of the element
•The bond strength.

Question 16

What happens to the melting points of period three metals (sodium to aluminium) as you progress through the period ?

Answer 16

•The melting point of each metal increases
•This is because of the greater positive charge of their ions (Na+ / Al3+)
•The additional electrons which are delocalised and the greater positive charge of the ion in Al results in a greater attractive force , meaning more energy is required to break the bonds of Al compared to Na.

Question 17

What is the trend in melting points from Na to Al ?

Answer 17

•The melting points of the period three metals increase as you progress
•This is because the ions formed by the metals have increasingly large charges (Na+ / Al3+)
•This means that more electrons are delocalised and the nucleus has a greater positive charge, resulting in a greater electrostatic force in Al compared to Na’s metallic bonding
•The stronger electrostatic force requires more energy to overcome, resulting in a higher mpt.

Question 18

Why does the melting point increase dramatically for Silicon in period 3 ?

Answer 18

•Silicon has a very strong covalent structure
•Therefore more energy is required to break the covalent bonds compared to van der waals, giving a higher mpt.

Question 19

Why does the melting point decrease in period three for phosphorus, sulphur and chlorine ?

Answer 19

•These molecules exist as simple covalent molecules held together by weak van der waals
•These bonds are easily broken so these molecules have a relatively low mpt.