AQA AS Chemistry Unit 1 Notes

I will be adding more topics as I go along.

Chapter 1 - Atomic Structure

• Note: AQA refers to protons and neutrons as fundamental particles (they are not), so I will do so too.
• Three fundamental particles comprise the atom:
• Protons: found in nucleus, relative mass of 1, relative charge of +1
• Neutrons: found in nucleus, relative mass of 1, relative charge of 0
• Electrons: found in orbitals outside of nucleus, relative mass 1/1840, relative charge of -1
• The nucleus is held together by the strong nuclear force (else proton-proton repulsions would shatter it instantly)
• As a general rule of thumb, the nth main electron energy level holds 2n^2 electrons.
• To draw electron 'dot and cross' diagrams, put the chemical symbol in the centre, surrounded by circles representing main energy levels with dots or crosses representing electrons.
• The first main shell consists of an s sub-orbital (s is spherical, will hold 2 electrons), called 1s.
• The second main shell consists of an s and THREE p sub-orbitals (p is dumbell/double-ice-cream-cone shaped, each holds two to give a total of 6)
• The third main shell consists of all of the same as in the second but with FIVE d sub-orbitals (four are clover shaped, the other is like a p orbital but with a ring around it, giving a total of 10)
• Fourth contains 7 f sub-orbitals extra, fifth contains 9 g orbitals extra, etc. etc.
• Electrons always fill sub-orbitals singularly before pairing occurs*
• Two electrons in the same orbital have opposite spins, represented by up/down arrows.
• The outermost electron is not necessarily at the highest energy level.  In terms of…