Unit 1

Question 1

In what way does electromagnetic radiation have a dual nature?

Answer 1

Has a wavelength and frequency but also exhibits particle-like behaviour.

Question 2

What is photon?

Answer 2

When electromagnetic radiation is absorbed or emitted by matter, it behaves more like a stream of particles than as a wave motion, these particles are called photons.

Question 3

What happens when a photon is absorbed?

Answer 3

Electrons within the substance gain energy.

Question 4

What happens when a photon is emitted?

Answer 4

Electrons within the substance lose energy.

Question 5

What happens when energy is transferred to an atom?

Answer 5

Electrons can be promoted to higher energy levels.

Question 6

How do electrons return to their original energy levels?

Answer 6

Energy must be lost from the atom.

Question 7

In what form is energy lost from an atom?

Answer 7

As a photon.

Question 8

How does atomic emmission spectra work?

Answer 8

Each line in an emission spectrum corresponds to the energy given out when an excited electron moves to a lower energy level.

Question 9

What does atomic emission spectra provide evidence for?

Answer 9

Discrete (quantised) energy levels in atoms.

Question 10

What are Atomic Emission Spectroscopy and Atomic Absorption Spectroscopy used for?

Answer 10

To identify and quantify the elements present in a sample.

Question 11

How are electrons promoted for an atomic absorption spectra?

Answer 11

By absorbing radiation.

Question 12

How is an absorption spectra produced?

Answer 12

By measuring how the transmission of light by the sample varies with wavelength.

Question 13

How are electrons excited for an atomic emission spectra?

Answer 13

High temperatures are used.

Question 14

What does the intensity of light emitted or absorbed represent in absorption and emission spectra?

Answer 14

The intensity of light is proportional to the concentration of the element present.

Question 15

What are the four quantum numbers?

Answer 15

• N, which tells us which shell the electron is in
• L determines the shape of the sub-shell (s,p,d,f)
• M determines the orientation of the orbital
• S indicates the spin of an electron within an orbital

Question 16

How many electrons can be held within a single orbital?

Answer 16

Two Electrons maximum.

Question 17

What is the Aufbau Principle?

Answer 17

The Aufbau principle states that electrons fill orbitals in order of increasing energy, meaning the lowest energy sub-shells are filled first.

Question 18

What are the order of orbitals in increasing energy?

Answer 18

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p

Question 19

What is meant by ‘Degenerate orbitals’?

Answer 19

Orbitals which have the same energy.

Question 20

What is Hund’s rule?

Answer 20

Hund’s rule states that when degenerate orbitals are available, electrons fill each degenerate orbital singly and with parallel spins, before pairing up to fill the orbitals.

Question 21

What is the Pauli Exclusion Principle?

Answer 21

The Pauli Exclusion Principle states that no two electrons in the one atom can have the same set of four quantum numbers.

Question 22

What is the consequence of the Pauli Exclusion Principle?

Answer 22

No orbital can hold more than 2 electrons and the 2 electrons must have opposite spins.

Question 23

What are the four blocks of the periodic table?

Answer 23

S block
P block
D block
F block

Question 24

How can variation in the first and second Ionisation energies of the first 36 elements be explained?

Answer 24

In terms of relative stability of different electronic configurations.

Question 25

What is the arrangement of electron pairs in a molecule when there are two bonding pairs?

Answer 25

Linear

Question 26

What is the arrangement of electron pairs in a molecule when there are three bonding pairs?

Answer 26

Trigonal Planar

Question 27

What is the arrangement of electron pairs in a molecule when there are four bonding pairs?

Answer 27

Tetrahedral

Question 28

What is the arrangement of electron pairs in a molecule when there are three bonding pairs and one lone pair?

Answer 28

Imperfect Tetrahedral

Question 29

What is the arrangement of electron pairs in a molecule when there are two bonding pairs and two lone pairs?

Answer 29

Imperfect Tetrahedral

Question 30

What is the arrangement of electron pairs in a molecule when there are five bonding pairs?

Answer 30

Trigonal Bi-pyramidal

Question 31

What is the arrangement of electron pairs in a molecule when there are six bonding pairs?

Answer 31

Octahedral

Question 32

How are the d-block transition metals described?

Answer 32

The d-block transition metals are metals with an incomplete sub-shell in at least one of their ions.

Question 33

Which two transition metals are exceptions to the Aufbau principle?

Answer 33

Chromium and Copper.

Question 34

How do transition metals lose electrons to form ions?

Answer 34

They lose the 4s electrons before the 3d electrons.

Question 35

When is an element said to be in a particular oxidation state?

Answer 35

When it has a specific oxidation number.

Question 36

What are the rules of oxidation numbers?

Answer 36

• The oxidation number of an uncombined element is 0.
• For ions containing single atoms (e.g Na+ or O2-) the oxidation number is the same as the charge on the ion.
• In most compounds, oxygen has oxidation number -2.
• In most compounds, hydrogen has oxidation number +1.
• Fluorine has oxidation number -1 in all its compounds.

-The sum of all oxidation numbers in a molecule or
neutral compound must add up to 0.

-The sum of all oxidation numbers in a poly-atomic ion must add up to the charge of the ion.

Question 37

What is Oxidation?

Answer 37

Oxidation is an increase in oxidation number.

Question 38

What is Reduction?

Answer 38

Reduction is a decrease in oxidation number.

Question 39

What makes a compound an oxidising agent?

Answer 39

Compounds containing metals in high oxidation states tend to be oxidising agents.