Topic 1- Atomic Structure

Question 1

What is the structure of an atom?

Answer 1

An atom has a nucleus containing protons and neutrons that is surrounding by orbiting electrons.

Question 2

What`s the relative charge and mass of a proton?

Answer 2

Have a relative charge of +1 and a relative mass of 1.

Question 3

What`s the relative charge and mass of a neutron?

Answer 3

Have a relative charge of 0 and a relative mass of 1.

Question 4

What`s the relative charge and mass of an electron?

Answer 4

Have a relative charge of -1 and a relative mass of 1/1836

Question 5

What`s the atomic number?

Answer 5

The number of protons in an atom.

Question 6

What`s the mass number?

Answer 6

The sum of the protons and neutrons in a nucleus.

Question 7

What`s an isotope?

Answer 7

Atoms of the same element with different numbers of neutrons.

Question 8

What`s relative atomic mass?

Answer 8

The weighted mean mass of an element relative to carbon-12.

Question 9

What`s relative isotopic mass?

Answer 9

The mean of an atom of an isotope of an element relative to carbon-12.

Question 10

What`s a TOF mass spectrometer?

Answer 10

An analytical instrument that gives information about relative isotopic mass and relative abundance of isotopes.

Question 11

What are the 5 stages in a TOF spectrometer?

Answer 11

1. Electrospray Ionization
2. Acceleration
3. Ion Drift
4. Ion Detection
5. Data Analysis

Question 12

What occurs in Electrospray Ionization?

Answer 12

A high voltage is applied to the sample. Molecules lose an electron and form gaseous positive ions.
- Molecules must be ionized so they can be accelerated and detected.

Question 13

How does Acceleration occur?

What ions reach the negative plate?

Answer 13

The cations are accelerated to a constant kinetic energy by passing through an electric field.

The lighter the ions the faster they travel.

Question 14

Describe Ion Drift

Answer 14

• This occurs in the flight tube where there`s no electric field.
• The ions are separated based on their speed; the smaller, fast ions travel through the flight tube most rapidly and reach the detector first.

Question 15

What happens at Ion Detection?

Answer 15

When the cations reach the detector they cause a small current due to their charge. The detector records the different flight times of the ions.

Question 16

What`s First Ionization Energy?

What`s the equation for first ionization energy?

Answer 16

This is the energy required to remove 1 mole electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

Question 17

What`s second Ionization Energy?

Answer 17

The energy required to remove 1 mole of electrons from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.

Question 18

What`s the trend in ionization energy down a group and why?

Answer 18

First Ionization energy DECREASES down a group because:
- Increase in atomic radius
- More shielding of the outer electron from the nuclear charge
- So less nuclear attraction for the outer electron and less energy required to remove it

Question 19

What`s the trend in ionization energy across a period and why?

Answer 19

First ionization energy INCREASES because:
- Increase in nuclear charge as go across
- Shielding is similar
- Smaller atomic radius so outer electron is held closer to nucleus through greater nuclear charge

Question 20

What`s the trend in successive ionization energies?

Answer 20

They get larger.
- More energy required to remove an electron from a +ve ion.
- Same number of protons for fewer electron so greater nuclear charge.