Unit 1- Atomic and electronic structure

Question 1

Define atomic numbers

Answer 1

Number of protons in an atom or ion

Question 2

Define mass number

Answer 2

Number of protons and neutrons in the nucleus

Question 3

Define isotopes

Answer 3

atoms of the same elements with the same atomic number but different mass number therefore same proton but different neutrons

Question 4

Define first ionisation energy

Answer 4

Amount of energy per mole to remove an electron from each gaseous atom to form a singly positive ion

Question 5

Define second ionisation energy

Answer 5

Energy change per mole for the removal of an electron from a singly positive ion to a doubly positive ion

Question 6

Define 1st electron affinity

Answer 6

Energy change per mole to add an electron to a gaseous atom to form a negative ion

Question 7

Define 2nd electron affinity

Answer 7

Energy change per mole to add an electron to a negative ion to a double negative ion

Question 8

Define orbitals

Answer 8

The region where an electron is most likely to be found within a shell

Question 9

Explain mass spectrometry

Answer 9

• Sample must be in a gaseous state
• Sample is injected into the machine and is vaporised
• Vapour is bombarded with high energy electrons therefore forming positive ions
• Ions are accelerated by an electric field
• Ions enter a magnetic field which deflects the ions
• Detector detects the ion

Question 10

What affects how much an ion is deflected?

Answer 10

• Mass of the ion- Heavier ions deflected less
• Charge of the ion- Smaller charge deflects less

Question 11

What does a mass spectrum show?

Answer 11

• Height of the peaks show abundance
• The peaks show the differnent isotopes present
• relative atomic mass = sum of (mass of each isotope x percentage of that isotope)/100

Question 12

What type of reaction is an ionisation reaction?

Answer 12

• Endothermic
• Energy required to put in

Question 13

What is proof of electron orbitals?

Answer 13

• Difference in ionisation energies to remove an electron

Question 14

Why is the ionisation energy for the final electron in a shell less?

Answer 14

• furthest from nucleus
• attraction weaker due to shielding
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Question 15

What do successive ionisation energy show?

Answer 15

• greatest jump between the ionisation energy show that electron is being removed from further position to the nucleus
• if the jump is greatest between the 4th and 5th electron therefore the element is group 4

Question 16

What are electron densities?

Answer 16

• Spread around the nucleus like a cloud
• Shows where the electron is most likely to be
• darker areas show a greater chance of an electron present
• p sub shell is spherical
• d sub shell are dumbells at right angles

Question 17

What is electron spin?

Answer 17

• Electrons can spin clockwise or anticlockwise in an orbital
• Two electrons cannot have the same spin due to repulsion

Question 18

What is periodicity?

Answer 18

• Repeating patterns in the periodic table
• They are repeating properties
• Similar for boiling points, ionisation energies and atomic radius

Question 19

What is the trend of atomic radius for the periodic table

Answer 19

• Down a group - Increases - Due to more electrons shells therefore more electron shielding so attraction is less
• Across the period- Decreases- Increasing number of nuetrons therefore greater positivity of the element. Due to same shell, held more tightly

Question 20

Explain the trend in ionisation energy for a period?

Answer 20

• Increase across a period- Increases positive charge without any extra electron shells therefore smaller radius so greater attraction beween the electron and nucleus
• Decreases down a group- More electron shells therefore more shielding therefore the attraction between the electron and the nucleus is less so less energy

Question 21

What three factors affect ionisation energy?

Answer 21

• Attraction between the nucleus and the outermost electron
• Size of the positive nuclear charge
• Extent of shielding

Question 22

What is the trend in melting temperature for a period?

Answer 22

• Group 1-3 - Increases due to more electrons increasing the strength of the bonds - metallic structure
• Group 4- Strong covalent bonds leading to very high melting temperatures- giant molecular structure
• Group 5-8- Simple molecules so low temperatures

Question 23

What affects melting temperatures?

Answer 23

Type of bonding and structure