3.1.1 Atomic Structure

Question 1

_____ take up most of the volume in atoms

Answer 1

Orbtitals take up most of the volume in atoms

Question 2

Relative mass for an electron

Answer 2

1/1840

Question 3

What letter represents the mass number?

Answer 3

A

Question 4

What letter represents the atomic number?

Answer 4

Z

Question 5

What type of ions have…

No. of electrons < No. of protons

Answer 5

Postive Ions

Question 6

What type of ions have…

No. of electrons > No. of protons

Answer 6

Negative Ions

Question 7

What holds the protons and neutrons?

Answer 7

Strong nuclear force

Question 8

What holds electrons and protons together in atom?

Answer 8

Electrostatic forces of attraction

Question 9

Why is the strong nuclear force stronger than electrostatic forces?

Answer 9

It overcomes repulsion between protons in nucleus

Question 10

Strong nuclear force acts only over very ___ distances

Answer 10

SHORT distances (within nucleus)

Question 11

What decides the chemical properties of an element?

Answer 11

No. & arrangement of electrons decides

Question 12

Why do isotopes have the same chemical properties? (2)

Answer 12

• ∵ they have same electron configuration
• chemical properties depend on electrons

Question 13

Isotopes have ___ _____ physical properties

Answer 13

slight different physical properties

Question 14

Why do isotopes have slight different physical properties?

Answer 14

∵ physical properties depend on mass of atom

Question 15

19th century: What did John Dalton say atoms were?

Answer 15

• Solid spheres
• Different spheres made different elements
• (All atoms of an element = same mass)

Question 16

1897: What did J.J. Thomson discover and what did it show?

Answer 16

• Discovered the electron
• Showed atoms weren’t solid and indivisible
• (Model known as ‘plum pudding model’)

Question 17

1909 - Ernest Rutherford: What did he find out?

Answer 17

Conducted the golden foil experiment:

• Fired positively charged alpha particles at a very thin sheet of gold
• Particles passed straight through gold & only small no. of particles were deflected backwards (pulm pudding model said = alpha particles would be deflected by the positive ‘pudding’ in atom)
• = developed into nuclear model of atom
  
  • Tiny positive nucleus surrounded by ‘cloud’ of negative electrons - most of atom is empty space

Question 18

What was Niels Bohr’s model & discovery?

Answer 18

• Model: where electrons exist in shells or orbits of fixed energy
• Discovered: When electrons move between shells, electromagnetic radiation (with fixed energy or frequency) is emitted/absorbed

Question 19

What have modern day scientists discovered & so what did they do?

Answer 19

• Electrons in same shell ≠ same energy
• Bohr model = wrong ∴ they refined it & added sub-shells
• (Isn’t perfect model but it’s simple and explains many experimental observations e.g. bonding & ionisation energy trends)

Question 20

What are relative masses essentially?

Answer 20

Masses of atoms compared to carbon-12

Question 21

Define Relative Atomic Mass (A_r) of an element (1x)

Answer 21

Average mass of an atom of an element on a scale where an atom of carbon-12 is 12

Question 22

Define Relative Isotopic Mass

Answer 22

Mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12

Question 23

Define Relative Molecular Mass (M_r)

Answer 23

Average mass of a molecule on a scale where an atom of carbon-12 is 12

Question 24

What does a mass spectrometer do and how?

Answer 24

• It determines the mass of separate atoms (or molecules)
• Works by forming ions from sample and then separating them according to the ratio of their charge to their mass

Question 25

Name the 6 things that happen when a sample is squirted into time of flight (TOF) mass spectrometer

Answer 25

1. Vacuum 2. Ionisation 3. Acceleration 4. Ion Drift 5. Detection 6. Data Analysis

Question 26

Describe the step vacuum in mass spectrometry (TOF)

Answer 26

Whole apparatus is kept under a vacuum to prevent ions produced from colliding with air molecules

Question 27

Name the two ways you can ionise your sample in mass spectrometry (TOF)

Answer 27

2 methods: 1. Electrospray ionisation 2. Electron impact ionisation

Question 28

Describe the method electrospray ionisation

Answer 28

1. A high voltage is applied to a sample in a polar solvent 2. Sample molecule, M, gains a proton forming MH⁺

Question 29

Describe the method electron impact ionisation

Answer 29

1. Sample is bombarded by high energy electrons 2. Sample molecule loses an electron = become +1 ions (M⁺)

Question 30

Describe the step acceleration in mass spectrometry (TOF)

Answer 30

Positively charged ions are accelerated by an electric field (attracted to negatively charged plate) so = they all have same kinetic energy

Question 31

Describe the step ion drift in mass spectrometry (TOF)

Answer 31

* Ions enter region with no electric field so they just drift through it * Lighter ions will drift faster than heavier ions

Question 32

Describe the step detection in mass spectrometry (TOF) & state how abundance is measured

Answer 32

* Lighter ions travel at higher speeds = reach detector in less time than heavier ions * Positive ions collected at detector * Causing current to flow / detected electrically * Abundance measured: idea that current depends on number of ions hitting detector

Question 33

Describe the step data analysis in mass spectrometry (TOF)

Answer 33

Signal from detector is sent to a computer which generates a mass spectrum

Question 34

What does the y-axis of mass spectrum represent?

Answer 34

Abundance of ions

Question 35

What does the height of each peak give on the mass spectrum?

Answer 35

Relative isotopic abundance

Question 36

If the sample is an element, what does each line represent on the mass spectrum?

Answer 36

A different isotope of the element

Question 37

What does the x-axis on the mass spectrum represent?

Answer 37

'mass/charge' ratio (m/z)

Question 38

Describe how to work out the relative atomic mass from mass spectrum (4)

Answer 38

1. Spectrum gives relative abundance (of isotopes) & m/z (mass/charge ratio) 2. Multiply m/z by relative abundance for each isotope 3. Sum these values 4. Divide by the sum of the relative iostopic abundances

Question 39

Why do elements with isotopes produce more than one line in a mass spectrum?

Answer 39

∵ isotopes = different masses

Question 40

Describe how you can use mass spectrometry to identify elements

Answer 40

You can see if the sample being analysed has the same relative abundances of isotopes

Question 41

Explain how you use mass spectrometry to identify molecules

Answer 41

mass/charge ratio (of peak) = relative molecular mass of molecule

Question 42

Electrons have ____ \_\_\_\_\_\_ & move around nucleus in certain regions of atom called \_\_\_\_\_\_\_\_\_\_\_\_

Answer 42

Electrons have fixed energies & move around nucleus in certain regions of atom called shells/energy levels

Question 43

Each shell is given a number called ____ \_\_\_\_ \_\_\_\_\_

Answer 43

principal quantum number

Question 44

What is the principal quantum number?

Answer 44

2(n²)

Question 45

The further away a shell is from nucleus, the _____ its energy & the ____ its principal quantum number

Answer 45

higher its energy + larger its principal quantum number

Question 46

Electrons in same the shell ___ have same energy

Answer 46

DON'T

Question 47

Shells divided up into sub-shells which have ____ \_\_\_\_\_\_ energies

Answer 47

slightly different

Question 48

Sub-shells have different no. of orbitals which can hold up to ___ electrons

Answer 48

2

Question 49

Answer 49

Question 50

2 electrons in each orbital...

Answer 50

spin in opposite directions

Question 51

Electrons fill up ___ energy sub-shell 1st

Answer 51

Electrons fill up lowest energy sub-shell 1st

Question 52

Why do electrons fill orbitals singly before they start sharing?

Answer 52

∵ electrons repel each other

Question 53

Electron configuration: Give 2 examples of transition metals behaving unusually

Answer 53

Chromium (Cr) & copper (Cu) = donate 1 of their 4s electrons to 3d sub-shell

Question 54

Write the electron configuration for chromium

Answer 54

Question 55

Write the electron configuration for copper

Answer 55

Question 56

Electron configuration: what happens when transition metals become an ion?

Answer 56

They lose 4s electrons before their 3d electrons

Question 57

Groups 4-7 can _______ electrons when they form _____ \_\_\_\_

Answer 57

Groups 4-7 can _share_ electrons when they form _covalent_ _bonds_

Question 58

Why are the gases in Group 0 inert?

Answer 58

∵ completely filled s & p sub-shells

Question 59

Why does Chromium (Cr) & copper (Cu) donate 1 of their 4s electrons to 3d sub-shell?

Answer 59

∵ they're happier with a more stable full or half-full d sub-shell

Question 60

Define first ionisation energy

Answer 60

Enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms

Question 61

Ionisation is a ________ process ∵ you have to put energy in to ionise atom/molecule

Answer 61

endothermic

Question 62

Write an equation for the first ionisation of oxygen

Answer 62

Question 63

Name 3 rules about ionisation energies

Answer 63

1. Must use gas state symbol (g) ∵ ionisation energies are measured for gaseous atoms 2. Always refer to 1 mole of atoms 3. Lower ionisation energy = easier it is to remove from ion

Question 64

Name 3 factors that affect ionisation energy

Answer 64

1. Nuclear Charge 2. Shielding 3. Distance from Nucleus

Question 65

Describe how nuclear charge affects ionisation energy

Answer 65

More protons in nucleus = more positively charged nucleus is & stronger the attraction for electrons

Question 66

Describe how shielding affects ionisation energy

Answer 66

As no. of electrons between outer electrons & nucleus increases = outer electrons feel less attraction towards nuclear charge Lessening of pull of nucleus by inner shells is called shielding (or screening)

Question 67

Describe how distance from nucleus affects ionisation energy

Answer 67

Attraction decreases rapidly with distance (i.e. electron close to nucleus = much more strongly attracted than one further away)

Question 68

What is meant by high ionisation energy?

Answer 68

High ionisation energy = high attraction between electrons & nucleus = more energy needed to remove electron

Question 69

What provides evidence for shells structure of atoms?

Answer 69

Graph of successive ionisation energies

Question 70

Within each shell, successive ionisation energies \_\_\_\_\_\_

Answer 70

increase

Question 71

Why does successive ionisation energies increase within each shell?

Answer 71

∵ electrons are being removed from an increasingly positive ion = less repulsion amongst remaining electrons ∴ they're held more strongly by nucleus

Question 72

When does big jumps in ionisation energy happen?

Answer 72

When a new shell is broken into = an electron is being removed from shell closer to nucleus

Question 73

Define second ionisation energy

Answer 73

Enthalpy change when 1 mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions

Question 74

State the equation for the second ionisation of oxygen

Answer 74

Question 75

State the equation for the *nth* ionisation energy

Answer 75

Question 76

Describe how you can use a successive ionisation energies graph to figure out which group an element belongs to

Answer 76

Count how many electrons are removed before the 1st big jump to find the group number

Question 77

Describe how you can use a successive ionisation energies graph to predict the electronic structure of elements

Answer 77

Working from right to left, count no. of points there are before each big jump to find how many electrons there are in each shell, starting with the first

Question 78

Name 2 trends in first ionisation energy

Answer 78

* 1st ionisation energies of elements down a group of periodic table decrease * 1st ionisation energies of elements across a period generally increase

Question 79

Explain why ionisation energy decreases down Group 2

Answer 79

1. Atomic radius increases/electron removed further from nucleus 2. As group is descended more shielding = nucleus' attraction reduces Both of these factors = make it easier to remove outer electrons = lower ionisation energy

Question 80

Explain why ionisation energy increases across a Period (2x)

Answer 80

1. Increased nuclear charge (no. of protons is increases = stronger nuclear attraction) 2. Extra electrons enter roughly same energy level or similar shielding

Question 81

Drops between Groups __ and ___ show _____ Structure

Answer 81

**Drops** between **Groups 2 and 3** show **Sub-Shell Structure**

Question 82

Describe and explain how aluminium provides evidence for the theory of electron sub-shells

Answer 82

1. Aluminium's _outer electron_ = in _3p_ orbital rather than 3s * ∵ 3p orbital = slightly higher energy than 3s orbital * ∴ electron is found f_urther from nucleus_ 2. _Additonal electron shielding_ - 3p orbital has additional shielding provided by 3s² electrons 3. Both these factors strong enough to override effect of increased nuclear charge = _ionisation energy drops slightly, easier to remove electron_

Question 83

Drops between Groups __ and __ Is due to Electron \_\_\_\_\_\_

Answer 83

**Drops** between **Groups 5 and 6** Is due to **Electron Repulsion**

Question 84

Describe and explain how phosphorus & sulfur provides more evidence for the eletronic structure model

Answer 84

1. (Shielding identical in phosphorus & sulfur atoms + electron is being removed from an identical orbital) 2. In phosphorus's case: electron being removed from singly-occupied orbital 3. But in sulfur: electron removed from _paired electrons in 3p orbital_ 4. _Electron repulsion_ between 2 electrons = _electron easier to remove from pair_

Question 85

Explain why the value of the first ionisation energy of neon is higher than that of sodium (2x)

Answer 85

* Electron removed from a level of lower energy or e– removed from 2p rather than from 3s * Less shielding

Question 86

Write the electron configuration for calcium using noble gas symbols

Answer 86

Question 87

Which of Na⁺ and Mg²⁺ is the smaller ion? Explain why (2)

Answer 87

Mg²⁺ Has more protons with same sheilding

Question 88

Magnesium exists as three isotopes: ²⁴Mg, ²⁵Mg & ²⁶Mg

Answer 88

²⁴Mg percentage = 80% ²⁶Mg percentage = 10%