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 the periodic table?

Answer 2

• the horizontal rows
• have the same number of electron shells

Question 3

what is a group on the periodic table?

Answer 3

• the vertical columns
• same number of outer electrons, this number indicated by the group number

Question 4

what are the 4 blocks of the periodic table ?

Answer 4

• s-block
• p-block
• d-block
• f-block

Question 5

what elements are in each block of the periodic table?

Answer 5

• s-block = groups 1 and 2
• p-block = groups 3 to 0
• d-block = transition metals
• f-block = radioactive elements .

Question 6

what is periodicity?

Answer 6

• the repeating pattern of trend in properties of elements across a period .
• often linked to elements electronic configurations.

Question 7

what is the trend in atomic radius along a period ?

Answer 7

• atomic radium decreases, along a period .

Question 8

why does the atomic radius decrease along a period ?

Answer 8

• atomic radius decreases due to increased nuclear charge for the same number of electron shells
• this means that the outer electrons are pulled in closer to nucleus because the charge produced a greater attraction.
• as a result , the atomic radius is reduced.

Question 9

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

Answer 9

• going down a group, atomic radius increases .

Question 10

why does atomic radius increase down a group?

Answer 10

• with each increment down a group, an electron shell is added.
• this increases the distance between outer electrons and nucleus , reducing the power of attraction.
• more shells also increases electron shielding, whereby inner shells create a “barrier” that blocks atttactive forces
• nuclear attraction is reduced further and atomic radius increases .

Question 11

what is the trend in ionisation energy along a period ?

Answer 11

• along a period, ionisation energy increases .

Question 12

why does ionisation energy increase along a period?

Answer 12

• increases as atomic radius decreases, hence nuclear change increases
• this means the outer electrons held more strongly so more energy required to remove outer electrons and ionise the atom.

Question 13

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

Answer 13

• going down a group, ionisation energy decreases.

Question 14

why does ionisation energy decrease going down a group?

Answer 14

• nuclear attraction between the nucleus and outer electrons reduces and shielding also increases
• both of these factors mean less energy needed to remove the outer electron .

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 happened to melting points across period 3 between sodium and aluminium?

Answer 16

• sodium, magnesium + aluminium = metals with metallic bonding .
• their melting points increase due to greater positive charge of their ions
• more electrons are released in the form of free electrons
• this increases atttactive electrostatic forces from Na to Al , this more energy needed to break them .

Question 17

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

Answer 17

• silicon has a very strong covalent structure .
• more energy needed to break strong covalent bonds - giving it a very high melting point.

Question 18

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

Answer 18

• phosphorus , sulfate + chlorine are simple covalent molecules held with weak van der waals forces
• less energy needed to overcome these weak intermolecular forces so these molecule have relatively low melting points .

Question 19

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

Answer 19

• argon is a noble gas that exists as individual atoms with a full outer shell of electrons
• makes atom very stable and van der waals forces between them very weak
• as a result, less energy needed to overcome these weak van der waals forces and so argon exists as a gas at room temperature .

Question 20

what’s the structure and function of graphite ?

Answer 20

• each carbon atom bonded to 3 others in plans hexagonal arrangement
• one of carbon other e- not used but delocalised so free to move through structure and carry a charge
• a layers of hexagons held together by weak intermolecular forces. (these forces break easily , separating layers from each other as slide over eachother)

Question 21

describe structure and function of graphene

Answer 21

• single layer of graphite and similar properties
• conduct electricity and high melting point / boiling point
• useful material in electronics + composite materials

Question 22

describe structure and function of diamonds .

Answer 22

• giant covalent structure = carbon atoms bonded to 4 other carbon atoms
• atoms held together by covalent bonds - diamond is hard and high melting and boiling point
• not able conduct electricity as not have any charged particles which are free to move .