Topic 1 - Atomic Structure and Periodic Table

Question 1

What is an isotope ?

Answer 1

Atoms of the same element with a different number of neutrons but the same number of protons

Question 2

What is relative atomic mass? (Ar)

Answer 2

the weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12

Question 3

What is relative isotopic mass?

Answer 3

mass of an atom of an isotope compared to 1/12th of the mass of an atom of carbon-12

Question 4

What is relative molecular mass (Mr)

Answer 4

average mass of a molecule compared to 1/12th of the mass of an atom of carbon-12

Question 5

What are orbitals, subshells and quantum shells ?

Answer 5

quantum shells = the energy levels surrounding nucleus

subshell = (in quantum) path taken by electrons as moves around nucleus

orbitals = (in subshell) most probable regions of an electron within a shell

Question 6

How many orbitals and electrons can each subshell hold ?

Answer 6

s subshell
- 1 orbital
- 2 electrons

p subshell
- 3 orbitals
- 6 electrons

d subshell
- 5 orbitals
- 10 electrons

f subshell
- 7 orbitals
- 14 electrons

Question 7

How many electrons in an orbital ?

Answer 7

2 electrons

Question 8

what is spin-pairing

Answer 8

when electrons in the same orbital have to ‘spin’ in opposite directions

Question 9

what is the shape of s-orbitals?

Answer 9

sphere

Question 10

what is the shape of p-orbitals

Answer 10

dumbell

Question 11

Write the order of electron configuration when 3d is not full

Answer 11

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² ( eg. 3d⁴ )

Question 12

What part of the periodic table is the s-block

Answer 12

Group 1 and Group 2

Question 13

What part of the periodic table is the p-block

Answer 13

Group 3 to Group 0

Question 14

What part of the periodic table is the d-block

Answer 14

transition metals

Question 15

Explain the exception of chromium and copper in terms of electronic configuration ? (write one out)

Answer 15

• they donate one of the 4s -electrons to the 3d subshell
• more stable with full or half full 3d subshell

chromium (Cr) :
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

copper (Cu) :
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹

Question 16

How does emission spectra support the idea of quantum shells

Answer 16

electron only exist in fixed orbits/shells

each shell has a fixed energy

when an electron moves between shells (gets excited) electromagnetic radiation is emitted or absorbed

energy of shells = fixed therefore radiation has fixed frequency

emission spectra show frequencies of light released

Question 17

what is ionisation

Answer 17

the removal of one or more electrons

Question 18

what is first ionisation energy

Answer 18

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

Question 19

what 3 factors affect ionisation energy and how

Answer 19

1. nuclear charge - more protons = stronger attraction
2. electron shells - attraction falls rapidly with distance
3. shielding =- number of electrons increases between outermost and nucleus = less attraction/pull

Question 20

what is the trend in ionisation energy

Answer 20

decreases down a group
increases across a period

Question 21

what is successive ionisation energy

Answer 21

when you remove an additional electron

Question 22

how does successive ionisation energy show shell structure

Answer 22

within a shell successive ionisation energies increase and more +ve ion = less repulsion

big jumps = new shell

Question 23

what is the trend for atomic radius

Answer 23

decreases across a period

Question 24

EXPLAIN the trend for atomic radius

Answer 24

number of protons increases = stronger pull to outer electrons

added electrons don’t affect as all added to same energy level across the period

Question 25

Why is there a drop in ionisation energy between G2/G3 rather than an increase ? (use example of magnesium and aluminium)

Answer 25

magnesium :
1s² 2s² 2p⁶ 3s²

aluminium:
1s² 2s² 2p⁶ 3s² 3p¹

1. Al outermost electron slightly higher energy level = further away from nucleus
2. 3p orbital has additional shielding

both factors = enough to override effect of nuclear charge

Question 26

Why is there a drop in ionisation energy between G5/G6 ? (use example of phosphorous and sulfur)

Answer 26

phosphorous:
1s² 2s² 2p⁶ 3s² 3p³

sulfur:
1s² 2s² 2p⁶ 3s² 3p⁴

shielding/distance = identical

therefore drop = electron repulsion
phosphorus - outermost removed from single occupied orbital
sulfur - removed from orbital with 2 electrons