CL 7- periodicity

Question 1

periodicity

definition

Answer 1

the repeating trend in chemical and physical properties across a period

Question 2

first ionisation energy

definition

Answer 2

the energy required to remove one mole of electrons from one mole of gaseous atoms

Question 3

first IE across periods 2 and 3

trend

Answer 3

• IE increases across a period
• atomic radius decreases
• stronger electrostatic attraction
• nuclear charge increases
• more energy required to remove outermost electron

Question 4

anomalies IE at group 3 and group 6

Answer 4

group3
* decrease in IE
* outermost electron in group 3 in p subshell which is
* higher in energy and further from the nucleus (than s subshell)
group6
* decrease in IE
* electrons begin to pair in p subshell in group 6
* repulsion between paired electrons making 6th electron slightly easier to remove

Question 5

IE down a group

trend

Answer 5

• IE decreases down group
• atomic radius increases
• (nuclear charge increases but)
• weaker electrostatic attraction
• less energy required to remove outermost electron

Question 6

metallic bonding

definition

Answer 6

electrostatic attraction between positive ions and delocalised electrons

Question 7

solid giant covalent lattice

Answer 7

atoms are held together by a network of strong covalent bonds in a giant lattice structure

Question 8

why do metals have high melting points?

Answer 8

strong electrostatic attraction between positive metal ions and delocalised electrons which require a lot of energy to overcome

Question 9

why are metals not soluble?

Answer 9

metals react with water instead of dissolving

Question 10

why do metals conduct electricity?

Answer 10

delocalised electrons free to move

Question 11

why do giant covalent compounds have high melting points?

Answer 11

strong covalent bonds which require a lot of energy to overcome

Question 12

why are giant covalent compounds not soluble?

Answer 12

covalent bonds very strong, can’t be broken by interaction with solvents

Question 13

variation in melting points across period 2/3

every group

Answer 13

increases from group 1 to group 3- higher positive charge, more delocalised electrons, stronger metallic bonding which require more energy to overcome
group 4- giant covalent structures so even higher increase, more energy required to overcome strong covalent bonds
decreases group 5- simple covalent structure, london forces require little energy to overcome. however the bigger the molecule the higher the melting point (S8 has higher melting point than P4)