Module 2: Atomic Structure & Ionisation Energies

Question 1

What is the Atomic number?

Answer 1

Number of protons in the nucleus of an atom.

Question 2

What is the Mass Number?

Answer 2

The total number of protons and neutrons in the nucleus of one atom of the element.

Question 3

What is an Isotope?

Answer 3

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

Question 4

What are the chemical properities of Isotopes?

Answer 4

• Isotopes have the same chemical characteristics as the atoms of the same element.
• This is because they have the same number of electrons in their outer energy level.

Question 5

What was the Mass Spectrometer used for?

Answer 5

• Used to discover isotopes.
• Uses the principle that heavier ions are deflected less than lighter ones when passed through a magnetic field.

Question 6

What are the 5 stages of the Mass Spectrometer?

Answer 6

1. Vaporisation-the element sampled must be heated until it turns into a gas of single atoms.
2. Ionisation-the sample is bombarded with high energy electrons from an elecron gun. These can knock out an electron from the sample to form a gaseous positive ion.
3. Acceleration-The passing of the ions through an electric field makes them accerlate to a certain speed.
4. Deflection-The ions are deflected by passing through a strong magnetic field. The amount of deflection depends on the mass-to-charge ratio. The smaller the m/z ratio the greater the deflection.
5. Detection-Ions hit the detector in the mass spectrometer and produce an electric current, this current is proportional to the number of ions collected. The information is fed into a computer or displayed in a chart.

Question 7

Relative Atomic Mass (Ar) formula

Answer 7

Ar=(Isotopic mass x abundance) / Total abundance

Question 8

Define the First ionisation energy

Answer 8

The energy required to remove 1 electron from each atom in a mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

Question 9

Explain the general trend of the 1st, 2nd, 3rd, etc ionisation energies

Answer 9

The ionisation energies increases because:
* Nuclear charge stays the same
* Shielding decreases
* So core charge increases
* Distance to outer electron decreases
* Hence nuclear attraction decreases

Question 10

Explain the general trend of the first ionisation energies as you go down a group

Answer 10

As we go down a group, ionisation energies decreases beacuse:
* Nuclear charge increases
* Shielding increases by the same amount
* So the core charge stays the same
* Distance to outer electron increases
* Hence nuclear attraction decreases

Question 11

Explain the general trend of the first ionisation energies as you go across a period

Answer 11

As we go across a period the ionisation energies increases because:
* Nuclear charge increases
* Shielding stays the same
* So core charge increases
* Distance to outer electron decreases slightly
* Hence nuclear attraction increases

Question 12

Eg. Between Mg and Al

What is the P-drop deviation?

Answer 12

In Aluminium the electron is lost from a 3p orbital, when ionised, which has a higher energy than the 3s in Magnesium.

Question 13

What is the pair-drop deviation?

Answer 13

When there is an orbital in the outer most energy level so the electrons experience extra repulsion. Hence it requires less energy to remove an electron from that orbital.

Question 14

What is an orbital?

Answer 14

A region of space where we find up to 2 electrons.

Question 15

Building principle

Answer 15

Electrons always fill the lowest energy orbitals first.

Question 16

Hund’s rule

Answer 16

Electrons never pair up in the same orbital until all orbitals of the same energy are singly occupied, and all unpaired electrons.