inorganic 1 - periodicity

Question 1

how are elements in the periodic table arranged?

Answer 1

elements are arranged according to their proton number

Question 2

what is a period on a 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 are the 4 blocks of the periodic table?

Answer 4

s,p,d,f blocks

Question 5

what elements are in each block of the periodic table?

Answer 5

s blocks - group 1 and 2
p block - group 3 to 0
d block - transition metal
f block - radioactive element

Question 6

what is periodicity?

Answer 6

the study of trends within the periodic table

Question 7

what is the trend in atomic radius along a period?

Answer 7

• along a period, atomic radius decreases

Question 8

why does atomic radius decrease along a period?

Answer 8

• increases nuclear charge for the same number of electron shells.
  -This means the outer electrons are pulled in closer to the nucleus because the charge produces a greater attraction.

Question 9

what is the trend in atomic radius going down the group?

Answer 9

going down a group, atomic radius increases

Question 10

why does atomic radius increase going down a group?

Answer 10

• electron shell is added with each element going down the group
• this increases the distance between the outer electrons and the nucleus
  -more shells increase the shielding = inner shells become a barrier that blocks the attractive forces
• nuclear attraction is reduced further and atomic radius increases

Question 11

what is the trend in ionisation energy along a period?

Answer 11

• ionisation energy increases

Question 12

why does ionisation energy increase along a period?

Answer 12

• atomic radius decreases = hence nuclear charge increases
• this means that the outer electrons are held more strongly = more energy is required to remove the outer electron and ionise the atom.

Question 13

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

Answer 13

ionisation energy decreases

Question 14

why does ionisation energy decrease going down a group?

Answer 14

• the nuclear attraction between the nucleus and the outer electrons reduces and the shielding also increases
• this means less energy is required to remove the outer electron

Question 15

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

Answer 15

• structure of element
• bond strength

Question 16

what happens to melting point across period 3, between sodium and aluminium?

Answer 16

-Na,Mg, Al = metals with metallic bonding
Their melting points increase along period 3, due to greater positive charge of their ions.

-The bonds get stronger because the metal ions have an increasing positive charge , increasing number of delocalised electrons and a decreasing radius.

-This increases the attractive electrostatic forces from Na to Al, therefore more energy is needed to break them.

Question 17

why does the melting point increase dramatically for silicone in period 3?

Answer 17

• silicone has a very strong covalent structure
• a lot of energy is needed to break the strong covalent bonds = giving it a high melting point

Question 18

why does the melting point decrease in period 3 between phosphorus and chlorine?

Answer 18

Phosphorus, Sulfur and chlorine are all simple covalent molecules held by van der waals forces
less energy is needed to overcome these weak intermolecular forces = so they have low MP.

Question 19

why does argon have an even lower melting point than chlorine?

Answer 19

• noble gas that exists as individual atoms and full outers hell electrons
• this makes them very stable so VDW forces are very weak
• therefore less energy is needed to overcome these VDW forces = exists as gas at room temperature

Question 20

why is there a Dip at Al for Ionisation energy?

Answer 20

outer electron is in a 3p orbital, which is higher in energy than 3s. Electron is found further than the nucleus. 3s orbital provides shielding. Less energy is needed to remove the outer electron than Mg

Question 21

Why is there a dip at S for ionisation energy?

Answer 21

one 3p orbital contains 2 electrons = there is repulsion between paired electrons so less energy needed to remove on.