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Chemistry OCR A AS > Module 3.1.1 - Periodicity (w/ ionisation) > Flashcards

Module 3.1.1 - Periodicity (w/ ionisation) Flashcards

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1
Q

What does the periodic table show?

A

Patterns of chemical and physical properties

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2
Q

What are horizontal rows of elements called?

A

periods

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3
Q

What are vertical columns of elements called?

A

groups

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4
Q

How is the periodic table arranged?

A

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

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5
Q

What do elements arranged in periods show?

A

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

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6
Q

What is periodicity?

A

The repeating pattern of trend across different periods

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7
Q

What do elements in the same group show?

A
  • Have similar chemical and physical properties
  • their atoms have the same number of outer shell electrons
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8
Q

What are metalloids also known as?

A

semi-metals

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9
Q

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

A

They have the same outer shell electron configuration

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10
Q

What do chemical reactions involve?

A

Only involve electrons in the outer shell

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11
Q

What do elements in the same period have?

A

A common core of electrons

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12
Q

What are s-block elements?

A

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

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13
Q

What happens to atomic radii across a period?

A

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

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14
Q

What happens to atomic radii down a group?

A

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

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15
Q

What does the period number tell?

A

The number of shells the atom has

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16
Q

What does the group number tell?

A

The number of outer shell electrons

17
Q

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

A
  • 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
18
Q

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

A
  • Have a giant structure
  • The bonds that need to be broken are strong bonds between atoms/particles
19
Q

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

A
  • Have a simple structure
  • Bonds that need to be broken are weak intermolecular bonds between molecules
20
Q

What does the process of ionisation produce?

A

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

21
Q

What is first ionisation energy?

A

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

22
Q

Why is the outer most electron removed first in ionisation?

A

The electron experiences the least nuclear attraction

23
Q

What factors affect ionisation?

A
  • Nuclear charge
  • Distance of outermost electron from the nucleus
  • Electron shielding
24
Q

How does nuclear charge affect ionisation energy?

A
  • 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
25
Q

How does distance affect ionisation energy?

A
  • 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
26
Q

How does electron shielding affect ionisation energy?

A
  • 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
27
Q

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

A
  • 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
28
Q

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

A
  • 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
29
Q

Where does ionisation energy across a period show a decreases

A
  • group 2 and 3
  • group 5 and 6
30
Q

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

A
  • 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
31
Q

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

A
  • 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
32
Q

What is successive ionisation energy?

A

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

33
Q

What does a successive ionisation energy graph show?

A
  • 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
34
Q

Why does successive ionisation energy increase with ionisation number?

A
  • 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

Chemistry OCR A AS (27 decks)

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