AQA A-Level Chemistry - Atomic Structure

Plum Pudding Model

After the discovery of electrons, the theory of atoms by which electrons are located in a sea of dispersed positive charge

Sub-Atomic Particles

The fundamental particles; protons, neutrons and electrons

Nucleus

The central part of the atom containing protons and neutrons

Nucleons

The sub-atomic particles within the nucleus

Proton

A sub-atomic particle:

- Relative mass = 1

- Relative charge = +1

Contained within the nucleus

Neutron

A sub-atomic particle:

- Relative mass = 1

- Relative charge = 0

Contained within the nucleus

Electron

A sub-atomic particle:

- Relative mass = 1/1840

- Relative charge = -1

Surrounds the nucleus in orbitals

Strong Nuclear Force

The force that holds the sub-atomic particles in the nucleus, despite being like particles so should repel one another

Electrostatic Force

The force that holds protons and electrons together in the atom

Isotope

The same number of protons within the nucleus, the same number of electrons, but a varied number of neutrons within the nucleus. The element does not change and is chemically the same due to the same number of electrons interacting with other electrons and elements

Mass Number

Number of protons + number of neutrons.

Also known as nucleon number (Physics)

Atomic Number

Number of protons.

Also known as proton number

Carbon-14

A radioactive isotope of carbon

Octet Rule

When drawing electron orbitals, this must be the rule that is considered for MOST elements. e.g. Boron defies this rule

Time of Flight Mass Spectrometer

A device that measures the abundance of isotopes in a sample

Vacuum

The whole TOF:MS is kept under this condition to prevent interference of foreign particles

Ionisation

The sample is dissolved in a volatile solvent and pushed through a fine hollow point needle. This needle is connected to a positive high voltage supply, which rips off electrons from the sample. The solvent then evaporates to form single ions

Acceleration

The positive ions are attracted towards a negative plate. Lighter ions travel faster

Ion Drift

The ions pass through a hole in the negatively charged plate. This forms a bean of ions which travel across a flight chamber

Detection

When ions meet the detector (at different velocities due to their varies masses) the flight times are recorded as they hit a detector which causes a flow of current. This current enables the machine to identify how abundant that mass is

Data Analysis

The signal that is detected is sent to a computer which plots on a graph the abundance of that mass

Low Resolution

A TOF:MS that detects to one decimal place. This is a more common TOF:MS

High Resolution

A TOF:MS that detects to five decimal places. This is a less common TOF:MS

Mass/Charge Ratio

What data is plotted from a TOF:MS

TOF:MS

Abbreviation for time of flight mass spectrometer

Overall Isotope Present

[(m/z1 x abundance1) + (m/z2 x abundance2)...]

/ total abundance

Mini-Mass Spectrometer

A mass spectrometer that investigates a library of spectra to detect chemical weapons, drugs or explosives

s

The first sub-level, can hold 2 electrons

p

The second sub-level, can hold 6 electrons

d

The third sub-level, can hold 10 electrons

f

The fourth sub-level, can hold 14 electrons

Arrows

How to represent electrons in subshells

Spin

Each element in the same orbital must have an opposite -BLANK-

Ionisation Energy

The minimum enthalpy change required to remove one mole of electrons from one mole of an element in the gaseous state

Increase

The trend in first ionisation energies across a period

Electron has entered a higher energy sub-level

The reason for the first anomaly in first ionisation energy across a period. The first ionisation energy has a drop

Electron has paired up so has like charge repulsion

The reason for the second anomaly in second ionisation energy across a period. The first ionisation energy has a drop

Decrease

The trend in first ionisation energies down a group