Topic 1 Atomic Structure And Periodic Table

Question 1

State proton symbol, relative mass, relative charge and position:

Answer 1

p, 1, +1, nucleus

Question 2

State neutron symbol, relative mass, relative charge, position

Answer 2

n, 1, 0, nucleus

Question 3

State electron symbol, relative mass, relative charge, position

Answer 3

e-, 1/1840, -1, energy levels

Question 4

What is relative isotopic mass?

Answer 4

The mass of the isotope on a scale on which a carbon-12 atom has a mass of exactly 12 units.

Question 5

What is Relative atomic mass?

Answer 5

The Ar of an element is the mass of one of its atoms relative to 1/12th the mass of one atom of carbon-12

Question 6

Why is the relative atomic mass of an element frequently not a whole number?

Answer 6

The Ar of an element is the average mass of the isotopes taking into account each isotopes abundance.

Question 7

What is mass spectrometry?

Answer 7

It’s an accurate instrumental technique used to determine the relative isotopic mass and the relative abundance of each isotope.

Question 8

What is the Molecular ion peak (M peak)?

Answer 8

The peak with the highest mass-to-charge ratio.

Question 9

How does Time of Flight (TOF) Mass Spectrometry work?

Answer 9

It records the time it takes for ions of each isotope to reach a detector. Using this, spectra can be produced showing each isotope present.

Question 10

Describe the first step of TOF Mass Spectrometry?

Answer 10

Ionisation - A sample of an element is vaporised and injected into the mass spectrometer where a high voltage is passed over the chamber. Causing electrons to be removed from the atom (they are ionised) leaving +1 charged ions in the chamber.

Question 11

Describe the second step of TOF Mass Spectrometry?

Answer 11

Acceleration - These positively charged ions are then accelerated towards a negatively charged plate.

Question 12

Describe the third step of TOF Mass Spectrometry

Answer 12

Ion drift - The ions are then deflected by a magnetic field into a curved path. The radius of their path is dependent on the charge and mass of the ion.

Question 13

Describe the fourth step of TOF Mass Spectrometry?

Answer 13

Detection - When the positive ions hit the negatively charged detection play, they gain an electron producing a flow of charge. The greater the abundance, the greater the current produced.

Question 14

Describe the fifth step of TOF Mass Spectrometry?

Answer 14

Analysis - These current values are then used in combination with the flight times to produce a spectra print-out with the relative abundance of each isotope displayed.

Question 15

What happens if during the ionisation process a 2+ ion is produced?

Answer 15

It will be affected by the magnetic field producing a curved path of a smaller radius. As a result, it’s mass to charge ratio is halved and this is shown on the spectra as a trace at half the expected m/z value.

Question 16

Who developed the ‘Quantum theory’ and what does it state?

Answer 16

Planck developed it and it states that energy exists in fixed amounts called quanta.

Question 17

What did Bohr propose with use of the ‘Quantum theory’?

Answer 17

Bohr applied Planck’s theory to electrons. He proposed that electrons could only exist in fixed energy levels (quantum shells).

Question 18

What is the evidence for the current electronic configuration?

Answer 18

• Emission spectra provide evidence for the existence of quantum shells
• Successive ionisation energies provide evidence for quantum shells within atoms and suggest the group to which the element belongs to
• The first ionisation energy of successive elements provides evidence for electron sub shells

Question 19

What are orbitals?

Answer 19

Clouds of negative charge where electrons are held

Question 20

Names of the different types of orbitals and their shapes

Answer 20

S, P, D and F. S-orbitals are spherical. P-orbitals are dumb-bell shaped. D-orbitals come in various shapes.

Question 21

Each element corresponds to blocks within the periodic table. Why?

Answer 21

S-Block is group 1 and 2. D-Block is the transition metals. P-Block is groups 3-0. F-Block are elements that don’t fit in the table. Each element in their block has outer electrons in their respective orbital.

Question 22

What is spin?

Answer 22

Within an orbital, electrons pair up with opposite spin so that the atom is as stable as possible. Electrons in the same orbital must have opposite spins.

Question 23

State the 3 rules for writing the electronic configuration?

Answer 23

• The lowest energy orbital is filled first
• Electrons with the same spin fill up an orbital first before pairing begins
• No single orbital holds more than 2 electrons

Question 24

Exceptions for rules of electronic configuration:

Answer 24

If electron spins are unpaired and therefore unbalanced, it produces a natural repulsion between the electrons making the atom very unstable. If this is the case, the electrons may take on a different arrangement to improve stability.

Question 25

What is Pauli’s exclusion principle?

Answer 25

Two electrons can go in each orbital, providing they are of opposite spin

Question 26

Hund’s rule of maximum multiplicity

Answer 26

Placing two electrons in one orbital means that, as they are both negatively charged, there will be some electrostatic repulsion between them. Placing each electron in a separate orbital reduces the repulsion and the system is more stable.

Question 27

What is ionisation energy?

Answer 27

The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state. Measured in kjmol-1

Question 28

Pattern of effective nuclear charge on the periodic table

Answer 28

Across the period, it increases

Question 29

How to measure atomic radii

Answer 29

Dividing the distance between the two nuclei by two

Question 30

Which radius can be determined in noble gases?

Answer 30

Van der Waal’s since they exist as atoms which do not bond with other elements

Question 31

Why does the atomic radii decrease across a period?

Answer 31

• Number of protons in nucleus increases, therefore nuclear charge increases. Meaning attractive force between the nucleus and outer electrons increases.

Question 32

Atomic radius decreases and increases…

Answer 32

Atomic radius increases down the group and decreases across the period

Question 33

Electronegativity increases and decreases…

Answer 33

Electronegativity increases across the period and decreases down the group