Chemistry - States and Mixtures
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Define an ion
Charged particles formed from single or groups of atoms losing or gaining electrons
What is a cation
A positive ion - formed by LOSS of ELECTRONS
What is an anion
A negative ion - formed by GAIN of ELECTRONS
Why do atoms form ions
To obtain a full outer electron shell
What ion charge will a group 1 element form?
+1
What ion charge will a group 2 element form?
+2
What ion charge will a group 6 element form?
-2
What ion charge will a group 7 element form?
-1
What is the difference between an -ide and an -ate compound?
-ide compounds contain only 2 elements -ate compounds contain 3 elements, one for which MUST be OXYGEN
What charge overall will an ionic compound have?
Zero - the total positive and negative charge MUST be the same
What type of structure do ionic compounds form?
Giant ionic lattice
Why do ionic compounds have high melting/boiling points?
Strong electrostatic forces between oppositely charged ions requires lots of energy to break
Why do ionic compounds conduct when in liquid/aqueous (water) but not solid?
When solid, the ions are in fixed positions and can’t move. When liquid/aqueous, the ions are free to move and can carry an electric charge
How is a covalent bond formed?
When pairs of electrons are shared between atoms
Why do simple molecular substances have low melting/boiling points?
The intermolecular forces of attraction between the molecules are weak and do not need much energy to be broken
Why don’t simple molecular substances conduct electricity?
They don’t contain any free moving charged particles (electrons or ions)
What is a polymer?
Long chains of carbon atoms covalently bonded together formed when monomers join together
What are the properties of a diamond?
Hard and strong (used in cutting tools) Strong covalent bonds in rigid lattice structure High melting point due to strong covalent bonds Needs lots of energy to break strong covalent bonds Poor conductor of electricity as it has no free moving charged particles (electrons or ions)
What are the properties of graphite?
Soft and slippery due to weak forces between layers (layers slide easily) High melting point due to strong covalent bonds in layers Needs lots of energy to break covalent bonds Good conductor of electricity as each carbon atom only forms 3 covalent bonds, so each carbon atom has one electron that is delocalised
Give 2 similarities and 2 differences between the properties of diamonds and graphite
Similarities 1) High melting point due to strong covalent bonds 2) Needs lots of energy to break strong covalent bonds Differences 1) Diamond is a poor conductor of electricity 2) Graphite is a good conductor of electricity
What type of structure do metals form?
Giant metallic lattice - cations surrounded by delocalised ions
Why are metals malleable? (malleable means can be changed into a new shape by beating with a hammer for example)
The layers of atoms can slide over each other
Why do most metals have high melting points?
Strong electrostatic forces between cations and delocalised electrons require a lot of energy to break.
Why are metals good conductors of electricity?
Delocalised electrons are free to move and can carry an electric charge