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Chemistry > Chapter 1 - Atomic Structure > Flashcards

Chapter 1 - Atomic Structure Flashcards

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1
Q

Define Atomic number

A

Atomic number is equal to the number of protons in the nucleus of an atom

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2
Q

Define Mass Number

A

The total number of protons and neutrons in the nucleus of an atom

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3
Q

Define Relative Atomic Mass

A

The average mass of an atom of an element relative to 1/12 the mass of an atom of carbon-12

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4
Q

What is an Isotope?

A

An atoms of the same element which have different mass number (different n. of neutrons same n. protons)

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5
Q

Define Relative Isotopic Mass

A

The mass of a single isotope of an element relative to 1/12 the mass of an atom of carbon-12

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6
Q

How do you calculate Relative Atomic Mass?

A

(Mass n. x abundance) + (Mass n. x abundance) / 100

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7
Q

Fill in
atomic n | mass n. | protons | Neutrons | Electron
31 | | | | |
P

A 
Atomic n. =15
Mass n.= 31
Protons = 15
Neutrons = 16
Electrons =15
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8
Q

Question:
The element magnesium (RAM=24.3) has three naturally occurring isotopes, Mg(24), Mg (25) and Mg(26). If the percentage of the heaviest isotope is 11.0%, what is the percentage of the lightest isotope present?

A

Mg (24) = 81%
Mg (25) = 8%
Mg (26) = 11%

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9
Q

Name the electron orbitals

A

1s2 - 2s2 - 2p6 - 3s2 - 3p6 - 3d10 - 4s2 - 4p6 - 4d10

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10
Q

Name the two exceptions with the electron orbitals

A

Chromium: 4s1 - 3d5 instead of 4s2 3d4

Copper: 4s1 - 3d10 instead of 4s2 - 3d9

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11
Q

What do the peaks on a Mass Spectrum of an element mean?

A

The different isotope ions in the element

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12
Q

What do the peaks on a Mass Spectrum of a compound mean?

A

The different fragment ions of the molecule

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13
Q

Analyse a Mass spectrum of an element

A

The n. of peaks = n. of isotopes in the sample

Relative heights = the abundances of each isotope

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14
Q

What are the different peaks in a mass spectrum of a compound

A

Largest peak is the BASE PEAK = caused by the most stable ion formed as the molecule breaks up

Other peaks are caused by the molecule fragmenting

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15
Q

In a Mass spectrum with chlorine what are the ions detected?

A 
Cl (35+)
Cl (37+)
Cl (35) -- Cl (37)
Cl (35) -- Cl (35)
Cl (37) -- Cl (37)
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16
Q

What is the relative ratio of isotopes of Cl 35 and 37 ?

A

3:1 Cl (35) :Cl (37)

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17
Q

What is the ratio of peaks at m/z values of 70:72:74?

A

9:6:1

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18
Q

In a Mass Spectrum of a compound which peak is the molecular ion?

A

The last major peak at the highest m/z value

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19
Q

How is the molecular ion peak written as?

A

M+

20
Q

How can a student identify an unknown compound after the mass spectrum?

A

Information about the peak heights and m/z values are inputted into computer.

Computer compares this info to those of its data bank and it can identify it.

Exact match is needed (like fingerprint)

21
Q

What is a subshell?

A

an orbital or a combination of orbitals

22
Q

How do metal atoms lose electrons to become ions?

A

They lose them from their most outer level, except of d block elements lose their 4s electrons first then 3d

23
Q

What does isoelectric mean?

A

Particles that have the same electron configuration

(e.g. neon and oxide ion O2-

24
Q

Definition of first ionisation energy

A

The energy required to remove one electron from each atom in a mole of gaseous atoms to give one mole of gaseous ions with a +1 charge

25
Q

When writing ionisation energy equations what are the state symbols?

A

ALWAYS (g)

26
Q

What is successive ionisation?

A

To continue removing electrons from an atom/ion until there are none left

27
Q

What are the three factors that affect successive ionisation energy?

A
  • Atomic radius
  • Shielding of the outer electron from the nucleus
  • Nuclear charge (how many protons)
28
Q

How does the atomic radius affect successive ionisation energy?

A

Atomic radius increases down a group and decreases across a period

The further an outer electron is from the attractive power of the nucleus the less energy is required to ionise it

29
Q

A greater nuclear charge leads to…

A

a stronger attraction to the outer electron so more energy is required to ionise it

30
Q

What does shielding mean?

A

How many electrons are between the nucleus and the outer electron so shielding the attractive power of the nucleus

31
Q

Does shielding increase or decrease the ionisation energy?

A

The more shielding the less power the nucleus exerts therefore the energy to knock of the outershell electron decreases

32
Q

First ionisation energy ….. down a group

A

Decreases DESPITE THE INCREASE IN NUCLEAR CHARGE

  • As you go down the group the atomic radius increases so outer electron more easily removed
  • As you go down the group shielding increases so attraction of the nucleus decreases so the outer electron is removed more easily
  • The nuclear charge increases as you go down group (works against other factors) so attractive force of the nucleus and outer shell electron increase.
33
Q

First ionisation energy …. across a period

A

Increases:

  1. Nuclear charge increases across period, increasing the attractive force between the nucleus and the outer shell electron
  2. Radius decreases, outershell electron is closer to the nuclear therefore the force of attraction increases
  3. Shielding remains almost constant bc the number of filled shells stays around the same
34
Q

There is a …. ionisation energy than expected for elements in group .. and … because ..

A

Lower, 3 and 6

Group 3 atoms have an s2 p1 arrangement, the outer p1 electron is further from the nucleus

Inner s2 electrons increase shielding so less energy is required to ionise the outer p1 electron

Group 6 atoms have a p4 arrangement- the repulsion of two electrons in the same p orbital leads to less energy required for ionisation

35
Q

A group 1 element has the (highest/lowest) first ionisation energy and the (highest/lowest) second IE

A

Lowest , highest

36
Q

The mass spectrometer is used to find what? (2 marks)

A
  • Find the abundance and mass of each isotope in an element to determine its RAM
  • Find the relative molecular mass
37
Q

Describe and explain the first stage of the mass spectrometry using electron impact

A
  • sample is vaporised and then high energy electrons are fired at it
  • High energy electrons come from an ‘electron gun’
  • Electron gun knocks off one electron from each particle forming a 1+ ion
  • The 1+ ions are attracted towards the neg. electric plate where they are accelerated
38
Q

When is the electron impact method used?

A

For elements and substances with low formula mass, often fragmentation occurs

39
Q

Describe and explain the first stage of the mass spectrometry using electrospray

A
  • Sample is dissolved in a volatile solvent and injected through a fine hypodermic needle to give a fine mist
  • Tip of needle is attached to the positive terminal of a high-voltage power supply
  • Particle are ionised by gaining a proton
  • Solvent evaporated away while the XH+ ions are attracted towards a neg. plate, where they are acceler.
40
Q

When is electrospray used?

A

Substances with higher molecular mass including proteins. Bc fragmentation rarely happends

41
Q

Why are the positive ions accelerated?

A

So that they all have the same kinetic energy

42
Q

Formula for KE

A

KE= 1/2 m x v 2

43
Q

Describe what happens in the drift tube/flight tube

A

Given that all the particle have the same KE the velocity of each particle depends on its mass.

Lighter particles have a faster velocity

The positive ions travel through a hole in the negatively charged plate into a tube

44
Q

What is the time of flight calculation?

A

t= d (square root) m/2KE

45
Q

Describe the events following detection

A

The positive ions hit the negatively charged electric plate

When they hit the detector plate, the positive ions are discharged by gaining electrons from the plate

This generates a movement of electrons and hence an electric current is measured (size of current gives a measure of n. of ions hitting the plate)

46
Q

What does m/z mean?

A

The mass to charge ratio (charge is always +1 so mass/1)

47
Q

Ionisation by electron impact causes removal of one electron from each particle. Write an equation for the species loss in C2H6

A

C2H6 + e- —> C2H6+ + 2e-

Chemistry (7 decks)

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