AQA AS Chemistry notes (Unit 1).

Pretty much a condensed version of the Nelson Thornes text book. I went through the book and picked out all the important parts of the book, and left all the unnecessary bits. Some of the bits in the text book are extremely vague and don't go into enough detail, so I have used parts of the CGP Complete revision and practice guide. These notes are intended for revision, so they require you to have a back ground knowledge of the topics already. Hope they are helpful, let me know what you think :D

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Atomic Structure

1.1 Fundamental particles.
Nucleus: The tiny, positively charged centre of an atom composed of protons and neutrons.

Nucleons: Protons and neutrons ­ the subatomic particles found in the nuclei of atoms.

Strong nuclear force: The force that holds protons and neutrons together within the nucleus
of the atom.…

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1.2 The arrangement of the electrons
Electron shells:

The shell closest to the nucleus fills first.

First shell holds up to 2 electrons

Second shell holds up to 8 electrons

Third shell holds up to 18 electrons

Electron diagrams:

We can write electron diagrams in short hand.

Step 1: Write…

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1.3 Mass number, atomic number and isotopes
Proton number: The number of protons in the nucleus of an atom, the same as the atomic number.

Mass number and atomic number:

The atomic number is the number of protons. As the number of protons is the same as the number of…

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1.4 The mass spectrometer

The mass spectrometer determines the mass of separate atoms (or molecules). They can be used to
identify substances such as illegal drugs.

The layout of a mass spectrometer:

What happens in a mass spectrometer?

Atoms are converted into ions, accelerated and deflected according to their masses…

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Mass spectra of elements:

The mass spectrometer can be used to identify different isotopes that make up an element.

It detects individual ions, so different isotopes are detected separately as they have different masses.

Low resolution mass spectrometry:

From the diagram above, the mass spectrum of neon has produced two…

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Energy levels:

Electrons in different shells have differing amount of energy.

These can be represented on an energy level diagram.

Shells are called main energy levels.

The first level only has a sublevel of s. The other sublevels used are p, d and f.

Atomic orbitals:

An electron is no…

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These shapes represent a volume of space in which there is a 95% probability of finding an
Any single atomic orbital can hold a maximum of two electrons.
Porbitals can hold up to two electrons each, but always come in groups of three of the
same energy level. This…

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Atomic orbitals of lower energy are filled first ­ so the lower main level is filled first, and
within this level, sublevels of lower energy are filled first.
Atomic orbitals of the same energy fill singly before pairing starts. This is because electrons
repel each other.
No atomic orbital can…

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1.6 Electron arrangements and ionisation energy.
Ionisation energy: the energy required to remove a mole of electrons from one mole of atoms in
the gaseous state.

Ionisation energy:

Electrons can be removed from atoms by hitting the atoms with a beam of electrons.

The energy it takes to do this…

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Ionisation energies tend to increase across a group because the nuclear charge increases.

In period 3 the increase is not regular.

The ionisation energy from
magnesium to aluminium goes down, despite an increase in nuclear charge.

This is because the outer electron in aluminium is in a 3p orbital. This…




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