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chemistry - Coggle Diagram
chemistry
redox reactions
in a redox reaction, reduction is a decrease in oxidation number, and oxidation is an increase in oxidation number
reactive metals react with many acids in redox reactions. The metal is oxidised to form a positive ion, and the hydrogen is reduced forming the element hydrogen gas
metals are commonly the reducing agent (give electrons) and non-metals are often the oxidising agent (gains electrons)
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oxidation numbers
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an oxidation number is a measure of the number of electrons that an atom uses to bond with atoms of another element
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exeptions
in peroxides, oxygen has an oxidation number of -1
when bonded to metals in hydrides, hydrogen has an oxidation number of -1
when bonded to fluorine, oxygen has an oxidation number of +2
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enthalpy
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the chemical system refers to the atoms, molecules or ions making up the chemicals
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ionisation energy
an ionisation energy requires energy, so it is endothermic, meaning all ionisation energies are positive
each time an electron is removed, there is a successive ionisation energy
each ionisation energy is higher than the last because there is less repulsion between the remaining electrons, so the electrons are drawn closer to the nucleus. As distance from the nucleus decreases, nuclear attraction increases
the first ionisation energy is the energy needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous +1 ions
across a period
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protons and nuclear charge increases, shielding is constant, greater nuclear attraction, atomic radius decreases, harder to remove electron, IE increases
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down a group
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atomic radius increases, shielding increases, nuclear attraction decreases, easier to remove electrons, IE decreases
noble gases have the highest ionisation energy. In general there is an increase in ionisation energy across the period and as we go down the group, ionisation energy will decrease
metallic bonding
metallic bonds are the strong electrostatic attraction between cations and elocalised electrons. cations are fixed to help maintain structure and shape. Delocalised electrons are mobile and an move thoughout the structure
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giant covalent
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giant covalent structure have high melting and boiling points due to a large amount of eenrgy being required to break strong covalent bonds in all directions
melting point of giant structures increases down a period due to an increase in size and attraction (group 1-14)
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