Atomic Structure

This series of lectures will cover:

Composition of matter - atoms, molecules and the periodic table
Structure of atoms - atomic models and radioactivity
Atomic mass, moles, chemical formulae and equations

Atomic structure:

Elements are made of atoms
Atoms are formed of a positive nucleus containing protons and neutrons. This is surrounded
by a negative electron shell
The atomic number for an element is the number of protons (and electrons) it contains
When describing the atomic structure
- A represents the mass number (total number of protons and neutrons)
- Z represents the number of protons/electrons and the atomic number

Isotopes are atoms of the same element with the same atomic number, but a different number

of neutrons, resulting in a different atomic mass.

Radioactive isotopes are unstable elements which have decreased nuclear binding (meaning they decay over time). This process of decay gives off radiation.

Ions are formed when an atom loses or gains electrons, meaning it is no longer neutral and has an overall net charge.

Electron configuration:

Electron shells are divided into discrete energy levels
The maximum number of electrons in a shell is 2n2 where n is the shell number
Electrons are held in different clouds called orbitals
- Orbitals show standing probability of where the electrons are likely to be found
- Orbitals can only contain electrons in opposite spin states (shown by arrows)
- Electrons fill the orbital according to subshell energy levels so s is first, then p, d and f

The Periodic Table sorts elements by atomic number and groups elements with similar properties and reactivity (this is determined by the electron shell configurations)