Atomic Structure pt1

Question 1

Where are electrons positioned within an atom? (1)

Answer 1

Electrons are located in orbitals within subshells around the nucleus of an atom.

Question 2

What are the physical and chemical properties of isotopes? (2)

Answer 2

• Isotopes have slightly different physical properties because of their different masses.
• They exhibit similar chemical properties since they have the same electronic configuration.

Question 3

What was John Dalton’s early model of the atom? (2)

Answer 3

• In the early 19th century, John Dalton described atoms as solid spheres.
• He suggested that different spheres represented different elements.

Question 4

Define RAM (Relative Atomic Mass)

Answer 4

Average mass of all isotopes of an element compared to 1/12 of the mass of carbon 12

Question 5

Define isotope

Answer 5

Atoms with the same number of protons but different number of neutrons.

They have the same chemical properties but different physical properties

Question 6

How many orbitals and electrons do these letters contain

S,P,D,F

Answer 6

S-1 orbital-2 electrons
P-3 orbitals-6 electrons
D-5 orbitals-10 electrons
F-7 orbitals-14 electrons (this one will rarely be used)

Question 7

What would be the relationship between 2 electrons in the same orbital in terms of their spin

Answer 7

• Opposite spin
• Repel each other

Question 8

What are the two elements that do not fit the trend for electronic configuration?

Answer 8

Copper (Ar 4s1 3d10)
Chronium (Ar 4s1 3d5)

They only fill one 4s orbital before filling out the 3d subshell

Question 9

Why is a mass spectrometer operated under a vacuum? (1)

Answer 9

To prevent air particles from becoming ionised and registering on the detector.

Question 10

When is electron impact used

Answer 10

For Elements or substances with low formula mass
It can also cause larger organic molecules to fragment

Question 11

When is electron spray used

Answer 11

For larger organic molecules

Question 12

True or false:
Fragmentation occurs in electrospray ionisation

Answer 12

False
It does not because the conditions are ‘softer’

Question 13

What is ionisation
(step 1)

Answer 13

The sample gets ionised (electrospray or electron impact)

Question 14

What are the steps in electron impact ionisation? (3)

Answer 14

1. A vaporised sample is injected at low pressure.
2. Then, an electron gun fires high-energy electrons at the sample, knocking out an outer electron.
3. This forms positive ions with different charges (e.g., Ti -> Ti⁺ + e⁻).

Question 15

What are the steps in electrospray ionisation? (4)

Answer 15

• (Sample is) dissolved (in a volatile solvent)
• (Injected through a) needle at high voltage/positively
  charged
• Each particle gains a proton/H+ in the form of a H+ ion X(g)+H^+–>XH+(g)
• The solvent evaporates whilst the ions move to the negative plate

Volatile- Flammable

Question 16

Why must the electrospray solvent be volatile and polar? (2)

Answer 16

• The electrospray solvent must be volatile so that it can evaporate easily, leaving ions to move towards the negative plate.
• It must also be polar so that it can supply molecules with hydrogen ions.

Question 17

What is the second step in TOF mass spectrometry? (3)

Answer 17

• Acceleration is the second stage of TOF mass spectrometry.
• This is when all positive ions are accelerated by an electric field generated by a negatively charged plate.
• Each ion is given the same kinetic energy

Question 18

Given that all the particles have the same kinetic enegry,Why do some particles go faster than others?

Answer 18

The velocity of the particls depends on its mass
Lighter particles have a faster velocity
Heavier particles have a slower velocity

Question 19

What is flight tube/ion drift(step 3)

Answer 19

• In the third stage, ions are separated based on their m/z values, even though they have the same kinetic energy.
• Ions with higher m/z values take longer to travel through the drift area.
• As a result, different ions have different flight times, which are recorded once they reach the detector.

m/z= mass over charge

Question 20

Formula for time of flight

Answer 20

t=d/v
T= time of flight (s)
d=length of flight tube (m)
v=Velocity of the partciles (ms^-1)

Question 21

What is detection(step4) (4)

Answer 21

• Ions reach the detector and each ion gains an electron from it
• This generates a small current
• The current is fed to a computer for analysis
• The size of the current is proportional to the abundance of the species

Question 22

Define Relative molecular mass (Mr)

Answer 22

Average mass of a molecule over 1/12 of the mass of a carbon 12

Question 23

What is the equation for an electron getting knocked off a sample

Answer 23

x(g)+e^- —> x^+(g) +2e^-

x is just any element

Question 24

For transition metals, when they are ionised which electron is removed fist in the sub shells? (only applies to d block elements)

Answer 24

the S block is removed first for example Fe is usually [Ar] 4s^2 3d^6
but Fe3+= [Ar] 3d^5

Question 25

What is the relative mass of an electron

Answer 25

1/1840

Question 26

Formula for Mass of an element

Answer 26

Ar/L=Mass (should be Ar/1000 if you wnat Kg) | L is avogodros constant

Question 27

What was J. J. Thomson's contribution to atomic structure? (2)

Answer 27

- In 1897, J. J. Thomson discovered the electron. - This showed that atoms were not solid and indivisible, leading to the 'plum pudding model' of a positively charged sphere containing electrons.

Question 28

What was Rutherford's gold foil experiment? (4)

Answer 28

1. In 1909, Rutherford fired positively charged alpha particles at a very thin sheet of gold. 2. Most alpha particles passed straight through, showing that most of the atom is empty space. 3. A few particles were deflected strongly, suggesting a small, dense, positively charged nucleus. 4. The plum pudding model was disproved and replaced by the nuclear model of the atom.

Question 29

What was the key idea of Rutherford's nuclear model? (2 marks)

Answer 29

- The atom contains a tiny, dense, positively charged nucleus. - This nucleus is surrounded by a cloud of negative electrons, with most of the atom being empty space.

Question 30

What was the problem with Rutherford's model and how did Bohr solved it? (3 marks)

Answer 30

- In Rutherford's model, electrons in a 'cloud' would spiral into the nucleus, making the atom collapse. - Niels Bohr proposed that electrons exist in fixed orbits (shells) at specific energies. - Movement between shells involves the emission or absorption of electromagnetic radiation of fixed frequency.

Question 31

Why was Bohr's model was accepted? (2)

Answer 31

- Bohr's model matched experimental observations of radiation absorbed and emitted by atoms. - This provided evidence that electrons occupy fixed energy levels.

Question 32

How was the Bohr model was refined? (2)

Answer 32

- It was later discovered that not all electrons in a shell have the same energy. - The model was refined to include sub-shells.

Question 33

What is a mass spectrometer used for? (2)

Answer 33

- A mass spectrometer is used to determine all the isotopes present in a sample. - It is also used to determine the elements or compounds within the sample.

Answer 34

What is relative isotopic mass? (1) Relative isotopic mass is the mass of a particular isotope of an element compared with carbon-12.

Question 35

What is the isotopic composition for chlorine and bromine? (2)

Answer 35

- The isotopic composition for Chlorine is 35Cl (75%), 37Cl (25%). - The isotopic composition for Bromine is 79Br (50%), 81Br (50%).

Question 36

What is the ratio of diatomic ions for chlorine and bromine? (2)

Answer 36

- The ratio of diatomic ions for Chlorine is 9:6:1. - The ratio of diatomic ions for Bromine is 1:2:1.

Question 37

What is a molecular ion? (1)

Answer 37

A molecular ion is the highest m/z peak on the mass spectrum.

Question 38

What must you remember when identifying the molecular ion with electrospray ionisation? (1)

Answer 38

You must subtract 1 from the m/z value to account for the H⁺ ion.

Question 39

What is the order in which atoms fill up with electrons? (1)

Answer 39

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶

Question 40

What is the rule for spin diagrams? (3)

Answer 40

Electrons fill orbitals singly before pairing up.

Question 41

What is the relationship between the position of the outer electron and the placement of the element on the periodic table? (2)

Answer 41

- The sub-energy level of the outermost electron determines the block in which an element is placed on the periodic table. - For example, sodium's outer electron is in the s sub-level, so sodium is located in the s-block.

Question 42

How do d-block elements lose electrons? (1)

Answer 42

D-block elements lose electrons from the 4s orbital before the 3d orbital.