Atomic Structure

Question 1

How does detection work in a mass spectrometer?

Answer 1

Lighter ions travel at higher speeds in the drift region, they reach the detector in less time than heavier ions. The detector detector charged particles and a mass spectrum is produced.

Question 2

Why does ionisation energy increases across the period?

Answer 2

This is because there is a greater number of protons which means there is a stronger nuclear attraction.

Question 3

How does electron shielding effect ionisation energy?

Answer 3

As the number of electrons between the outer electrons and the nucleus increases there is a greater distance and so a smaller nuclear attraction. This means there is a lower nuclear charge and so a lower ionisation energy.

Question 4

Draw a diagram of an atom, labelling each part.

Answer 4

See book

Question 5

What happens during ion drift in a mass spectrometer?

Answer 5

The ions into a region with no electric field, so they will just drift through. Lighter ions will drift through faster than heavier ones.

Question 6

Definition of relative isotopic mass:

Answer 6

Relative isotopic mass is the mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12

Question 6

Where is mass concentrated in an atom and what makes up most of its volume?

Answer 6

Nucleus makes up most of the mass

Orbitals make up most of the volume

Question 7

What does ionisation do in a mass spectrometer?

Answer 7

Electrospray ionisation - the sample is dissolved and pushed through a small nozzle at high pressure and high voltage is applied to it causing the particle to become a positive ion the sample is made into a gas made of positive ions

Electron impact ionisation - The sample is vaporised and an electron gun is used to fire high energy electrons this knocks one electron of each particle so they become +1 ions

Question 9

What does acceleration do in the mass spectrometer?

Answer 9

The positively charged ions are accelerated by an electric field so that they all have the same kinetic energy

Question 11

Why are there small drops of ionisation energy values in groups 2, 3, 5 and 6?

Answer 11

Because of sub-shells. For example in period 3 aluminiums outer electron is in a 3p orbital rather than a 3s. So the electron is further from the nucleus. The 3p orbital have shielding from the three stop these factors mean that the ionisation energy drops slightly. (Between groups 2 and 3)
This provides evidence for the theory of sub-shells.

Because of electron repulsion. For example the shielding is identical in both phosphorus and sulphur atoms the electron is being removed from the same orbital. With phosphorus the electron is being removed from a singularly occupied orbital however in Sulfur the electron is being removed from an orbital containing two electrons. The repulsion between 2 electrons in an orbital means the electrons are easier to move from shared orbitals.

Question 12

What are electrons?

Answer 12

Electrons have a -1 charge and sit around the nucleus in orbitals. These orbitals make up a majority of the volume of the atom.

Question 13

What is a nucleus?

Answer 13

The nucleus is where you find the protons and neutrons, it makes up most of the mass of the atom.

Question 14

What’s an isotope?

Answer 14

An isotope of an element are atoms with the same number of protons but different number of neutrons.

Question 14

Definition of relative molecular mass, Mr:

Answer 14

The relative molecular mass, Mr, is the average mass of a molecule on a scale where an atom of carbon-12 is 12.

Question 16

Definition of ionisation energy:

Answer 16

The first ionisation energy is the energy needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 17

Why does ionisation energy decreases down the group 2?

Answer 17

Each element down group 2 has an extra electron shell compared to the one above. This means electron shielding is taking place. Also the extra electron shell means out of electrons are further away so the nuclear attraction is reduced.

This means it is easier to remove outer electrons resulting in a lower ionisation energy.

Question 18

What are the main trends in first ionisation energy’s?

Answer 18

1) The first ionisation energy is of elements down a group decrease
2) first ionisation energy across a period generally increases

Question 19

What did J. J. Thomson discover?

Answer 19

He discovered the electron and showed that atoms weren’t solid and indivisible. This new model was known as the plum pudding model.

Question 20

What did Niels Bohr propose?

Answer 20

He proposed that electrons exist in shells or orbitals with a fixed energy. When electrons move between shells electromagnetic radiation is emitted or absorbed.

Question 21

What did Earnest Rutherford find?

Answer 21

He found that most of an atom is empty space surrounded by a ‘cloud of negative electrons’ with a tiny positively charged nucleus in the centre.

He discovered this by the gold foil experiment. Positively charged alpha particles were fired at a very thin gold sheet.

Question 21

How does nuclear charge affect ionisation energy?

Answer 21

Nuclear charge affects ionisation energy as when there are more protons in the nucleus the more positively charged the nucleus is and the stronger the attraction is. This means that the higher the nuclear charge the higher the ionisation energy.

Question 22

What did John Dalton believe about atoms?

Answer 22

He believed that atoms where solid spheres and so said that different spheres made up the different elements.

Question 22

Definition of relative atomic mass:

Answer 22

The relative atomic mass, Ar, is the average mass of an atom of an element on a scale where an atom of carbon-12 is 12.

Question 24

How does the distance from the nucleus affect ionisation energy?

Answer 24

The further away the electrons be easier it is to ionise atom. And electronic close to the nucleus will be more strongly attracted to the nucleus versus one that is further away

Question 25

Definition of the second ionisation energy:

Answer 25

The second ionisation energy is the energy needed to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.