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CHEM 1 Revision - Structure and
Bonding (Unit 1)
1. Atoms and elements
A substance that is made of only one type of atom is called an element. There are about 115
different elements.

Structure - Atoms have a small central nucleus made of positive particles called protons and
neutral…

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Radioactivity - If an element is unstable, it can collapse to make itself stable. When this process
emits radiation waves, it is called radiation or radioactivity.

Structure - An atom has several shells, in which only a certain number of electrons in each. The
first shell contains 2 electrons maximum,…

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(35 x (72/100)) + (37 x (28/100)) =

25.2 + 10.3 = 35.5 - this is the relative atomic mass.



3. Compounds

Compounds are made of more type of atom which are bonded together. The different atoms in
a compound are in a definite fixed ratio. They are substances in…

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In a metal, the metal cations are arranged in a close packed lattice surrounded by a sea of
mobile, delocalised, valence electrons. The strong electrostatic attraction between the positive
metal cations and the sea of mobile, delocalised, valence electrons is called a metallic bond.
Metallic bonding is the bonding of…

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Non-metal atoms gain electrons to form negative ions (also known as anions). These non-metal
anions often have noble gas configurations of electrons. Non-metal ions are usually negatively
charged.



The strong electrostatic attraction between positive ions and negative ions is called an ionic
bond.




This diagram is a dot and cross…

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Ionic compounds have high melting points and boiling points because a lot of energy is needed
to pull the ions in the lattice apart.

Ionic compounds cannot conduct as solids because the ions are not free to move in a solid lattice.
If the ionic compound is melted/molten or dissolved…

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