Atomic Structure pt1

Question 1

What does the atomic number represent and what letter is used to represent it

Answer 1

Number of protons in an atom
Z is the letter used to represent the atomic number

Question 2

What letter represents mass number

Answer 2

A

Question 3

How is mass number calculated

Answer 3

Number of protons + Number of neutrons= Mass number

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

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 does the mass spectrometer need to be under a vucuum

Answer 9

Because the air particles would ionise and register 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

How is electron impact done(4)

Answer 14

• A vaporuised sample is injected at low pressure
• An electron gun fires high energy electrons at the sample
• Which knocks out an outer electron
• Forming positive ions with diff charges

Question 15

How is electro spray ionisation done (5)

Answer 15

• The sample is dissolved in a volatile, polar solvent
• It is then injected through a fine needle giving a mist or aerosol
• The tip of the needle has a high volatage
• At the tip of the needle,it gains a proton from the solvent 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

What is acceleration (step 2 )

Answer 16

When positive ions are accelerated by an electric field to a constant kinetoc energy

Question 17

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

Answer 17

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

Question 18

What is flight tube/ion drift(step 3)

Answer 18

• The positive ions with smaller m/z values will have the same kinetic energy as those with a larger m/z and will move faster
• Heavier ions take longer to move through the drift area
• The ions are distingushed by diff flight times

m/z= mass over charge

Question 19

Formula for time of flight

Answer 19

t=d/v
T= time of flight
d=length of flight tube
v=Velocity of the partciles

Question 20

What is detection(step4)

Answer 20

• Ions hit detector and this causes a current which causes electron flow
• The size of the current is proportional to tge abundance of the isotope

Question 21

Define Relative molecular mass (Mr)

Answer 21

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

Question 22

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

Answer 22

x(g)+e^- —> x^+(g) +2e^-

x is just any element

Question 23

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

Answer 23

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

Question 24

What is the relative mass of an electron

Answer 24

1/1840