Atomic Structure

Question 1

What is an element’s mass number?

Answer 1

The total number of protons and neutrons in its nucleus

Question 2

What is an element’s atomic number?

Answer 2

Number of protons it has in its nucleus

Question 3

What are isotopes?

Answer 3

Atoms of the same element with different numbers of neutrons

Question 4

What are electrons arranged into?

Answer 4

Electron shells/ energy levels

Question 5

What are electrons divided up into?

Answer 5

Sub-shells/ sub-levels

Question 6

What are sub-shells divided up into?

Answer 6

Orbitals

Question 7

What are orbitals?

Answer 7

The area of space that electrons occupy - area which we are most likely to find electron in.

Question 8

How many electrons can an orbital hold up to?

Answer 8

2

Question 9

What is on an atom’s 1st energy level?

Answer 9

1 sub-shell
s sub-shell: 1 orbital
total electrons: 2

Question 10

What is on an atom’s 2nd energy level?

Answer 10

2 sub-shells
s sub-shell: 1 orbital
p sub-shell: 3 orbitals
total electrons: 8

Question 11

What is on an atom’s 3rd energy level?

Answer 11

3 sub-shells
s sub-shell: 1 orbital
p sub-shell: 3 orbitals
d sub-shell: 5 orbitals
total electrons: 18

Question 12

What are the rules for determining the electron configuration?

Answer 12

Lowest energy is filled first (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p)
Electrons should occupy orbitals on their own, only sharing an orbital if there are no empty orbitals of the same energy level

Question 13

Why is hydrogen difficult to place on the periodic table?

Answer 13

It is an s-block element with 1 electron in the s sub-level but has different properties to Group 1 elements

Question 14

Why is helium difficult to place on the periodic table?

Answer 14

It is NOT a p-block element but is placed with other noble gases because they share properties.

Question 15

When an ion forms,are the 3d or 4s electrons lost first?

Answer 15

4s

Question 16

Why would the electrons in the last orbital in an atom be the easiest to lose?

Answer 16

Has the weakest attraction to nucleus:
Has the furthest distance from nucleus
Positive charge of nucleus shielded by inner electrons

Question 17

What is the definition of ionisation energy?

Answer 17

Ionisation energy (IE) is the energy required to remove one mole of electrons from one mole of atoms in the gaseous state.

Question 18

What is ionisation energy measured in?

Answer 18

kJ mol−1

Question 19

What is magnesium’s first ionisation energy equation?

Answer 19

Mg (g) –> Mg+ (g) + e-

Question 20

Are ionisation energies always increasing?

Answer 20

Yes.

Question 21

What factors affect ionisation energies?

Answer 21

Distance from nucleus
Nuclear charge
Shielding (repulsion) by electrons in inner shells between nucleus and outer electron

Question 22

What is the trend in 1st ionisations as we go down group 2?

Answer 22

Ionisation energies decrease

Question 23

Why do 1st ionisation energies generally decrease down groups?

Answer 23

-Increase in size of atom (more energy levels occupied by electrons)
-‘Outer electrons further away from nucleus’
-‘Additional inner electrons shield the positive charge of nucleus’
‘ ‘ = Reduced attraction between electron + nucleus - less energy required to remove

Question 24

What trend would you expect to see in 1st IE’s across period 3?

Answer 24

General increase in IE

Question 25

Why do 1st IEs generally increase across periods?

Answer 25

An increased nuclear charge but no/little difference in shielding so there is a stronger attraction between the electron being removed and the nucleus

Question 26

Describe the Aluminium anomaly.

Answer 26

Aluminium has a lower 1st IE than Magnesium. The electron being removed from Al is in a 3p orbital whereas for Mg the electron is in a 3s orbital. The 3p orbital is higher in energy than 3s, so requires less energy to remove an electron from 3p

Question 27

Describe the Sulfur anomaly.

Answer 27

Sulfur has a lower 1st IE than Phosphorus. In S, there are a pair of electrons in a 3p orbital. These electrons repel each other, which makes it easier to remove one of them than P.

Question 28

What is Mass Spectrometry?

Answer 28

An analytical technique which allows us to determine the mass of molecules and elements.

Question 29

What are the four stages of Time of Flight mass spectrometry?

Answer 29

Ionisation Acceleration Drift region Detection

Question 30

What are the two types of ionisation in ToF?

Answer 30

Electron impact method Electrospray method

Question 31

What is the electron impact method used for?

Answer 31

Elements and low Mr compounds

Question 32

What is the electrospray method used for?

Answer 32

Used for elements and high Mr compounds (e.g. proteins)

Question 33

What is the equation for electron impact method?

Answer 33

X (g) --> X+ (g) + e- X (g) +e- --> X+ (g) + 2e-

Question 34

What is the equation for electrospray method?

Answer 34

X (g) + H+ --> XH+ (g)

Question 35

What happens in electron impact?

Answer 35

Substances lose an e- Mass remains the same

Question 36

What happens in electrospray?

Answer 36

Substances gain a H+ Mass increases by 1

Question 37

How do atoms form ions?

Answer 37

By gaining or losing electrons

Question 38

Why do isotopes have the same chemical properties?

Answer 38

They have the same electron configuration

Question 39

Why do isotopes have different physical properties?

Answer 39

Physical properties tend to depend more on the mass of the atom.

Question 40

Describe Dalton's model of the atom.

Answer 40

At the start of the 19th century, he described atoms as solid spheres and said that different spheres made up the different elements

Question 41

Describe Thomson's model of the atom.

Answer 41

In 1897, he discovered that an atom must have even smaller, negatively charged particles - electrons. Plum pudding model.

Question 42

Describe Rutherford's model of the atom.

Answer 42

Discovered that there was a tiny, positively charged nucleus at the centre, surrounded by a 'cloud' of negative electrons. Most of the atom is empty space.

Question 43

What are the factors affecting ionisation energy?

Answer 43

1. Nuclear charge 2. Distance from nucleus 3. Shielding

Question 43

Define the relative atomic mass.

Answer 43

The relative atomic mass is the average mass of an atom of an element compared to 1/12th of an atom of Carbon-12