Module 3.1.1 - Periodicity (w/ ionisation)

Question 1

What does the periodic table show?

Answer 1

Patterns of chemical and physical properties

Question 2

What are horizontal rows of elements called?

Answer 2

periods

Question 3

What are vertical columns of elements called?

Answer 3

groups

Question 4

How is the periodic table arranged?

Answer 4

Increasing atomic number (increasing number of protons in the nucleus)

Question 5

What do elements arranged in periods show?

Answer 5

Trends in physical and chemical properties across a period that are repeated across each period

Question 6

What is periodicity?

Answer 6

The repeating pattern of trend across different periods

Question 7

What do elements in the same group show?

Answer 7

• Have similar chemical and physical properties
• their atoms have the same number of outer shell electrons

Question 8

What are metalloids also known as?

Answer 8

semi-metals

Question 9

Why do elements in the same group react in a similar way?

Answer 9

They have the same outer shell electron configuration

Question 10

What do chemical reactions involve?

Answer 10

Only involve electrons in the outer shell

Question 11

What do elements in the same period have?

Answer 11

A common core of electrons

Question 12

What are s-block elements?

Answer 12

Have their highest energy outer shell electron in an s-orbital

Question 13

What happens to atomic radii across a period?

Answer 13

Atomic radii decreases from left to right
- Protons added to nucleus: nuclear charge increases
- Electrons added to the same shell
- Nuclear attraction on outer shell electrons increases across a period
- Electron shells are drawn inwards by the nucleus,making atoms smaller

Question 14

What happens to atomic radii down a group?

Answer 14

The atomic radii increases down a group
- The number of shells increase
- Outer electron added to a new shell which is further away from the nucleus
- Shielding effect by inner shell electrons increases down a group
- Increased distance of outermost electron from nucleus and shielding effect far outweigh the increase in nuclear charge
- Nuclear attraction decreases down a group

Question 15

What does the period number tell?

Answer 15

The number of shells the atom has

Question 16

What does the group number tell?

Answer 16

The number of outer shell electrons

Question 17

What happens across a period in terms of melting and boiling points?

Answer 17

• Increase gradually from group 1 to group 4
• Decrease sharply between group 4 and 5 (signifies a change in structure from giant to simple)
• are comparatively low from group 5 to group 8

Question 18

Why do groups 1-4 have a high melting and boiling point?

Answer 18

• Have a giant structure
• The bonds that need to be broken are strong bonds between atoms/particles

Question 19

Why do groups 5-8 have comparatively low melting and boiling points?

Answer 19

• Have a simple structure
• Bonds that need to be broken are weak intermolecular bonds between molecules

Question 20

What does the process of ionisation produce?

Answer 20

Ions with a positive charge
- electron is moved from the outer shell

Question 21

What is first ionisation energy?

Answer 21

The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 22

Why is the outer most electron removed first in ionisation?

Answer 22

The electron experiences the least nuclear attraction

Question 23

What factors affect ionisation?

Answer 23

• Nuclear charge
• Distance of outermost electron from the nucleus
• Electron shielding

Question 24

How does nuclear charge affect ionisation energy?

Answer 24

• More protons, the greater its nuclear charge
• Stronger the nuclear attraction on outer electrons
• Higher nuclear charge requires more energy to overcome attraction between nucleus and outermost electron

Question 25

How does distance affect ionisation energy?

Answer 25

- as distance between the nucleus and outermost electron increases, the attraction between them decreases - the weaker the nuclear attraction, less energy is needed to remove the outer electron

Question 26

How does electron shielding affect ionisation energy?

Answer 26

- electron shielding; the repulsion between electrons in inner shells - reduces the net nuclear attraction from positive nucleus on outer shell electrons - more shells, the greater the shielding effect and weaker the nuclear attraction

Question 27

What is the general trend down a group for 1st ionisation energy?

Answer 27

- First ionisation energy **decreases** - more shells, more shielding effect from inner shell electrons - atomic radius increases - increased distance from nucleus and increase shielding effect *far outweigh* increase in nuclear charge - nuclear attraction hence decreases on outer shell electrons - less energy is needed to remove the outer electron

Question 28

What is the general trend across a period for first ionisation energy?

Answer 28

- first ionisation energy shows a **general increase** across a period - the outer electron fills the same shell, shielding remains the same - the number of protons increases, nuclear charge increases - atomic radius decreases - hence a greater nuclear attraction on outer electrons - more energy needed to remove outer electron

Question 29

Where does ionisation energy across a period show a decreases

Answer 29

- group 2 and 3 - group 5 and 6

Question 30

Why is there a decrease in IE between group 2 and 3?

Answer 30

- the p sub-shell (group 3) has higher energy than s sub-shell (group 2) - the p electron needs less energy to be removed, giving it a lower 1st IE

Question 31

Why is there a decrease in IE between group 5 and group 6?

Answer 31

- there is an electron pairing in the p orbital in group 6 element - in the group 5 element, each p orbital contains one electron: one p orbital in group 6 element contains two electrons paired - the paired electrons repel each other, it is easier to remove one of these electrons - hence less energy needed

Question 32

What is **successive ionisation energy?**

Answer 32

A measure of the energy required to remove each electron in turn

Question 33

What does a successive ionisation energy graph show?

Answer 33

- shows the largest increase in ionisation energy; the electron has been removed from a new shell that is **closer to the nucleus and has less shielding from inner electrons** - shows how many electrons in outer shell; what group the element is in

Question 34

Why does successive ionisation energy increase with ionisation number?

Answer 34

- once an electron has been removed, there are the same number of protons but fewer electrons - proton:electron ratio increases - remaining electrons more strongly attracted to nucleus; more energy is needed to remove each electron in turn