Difference between revisions of "Chemical Formula"
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: '''Chemical Formulae''' show which [[element]]s are in a [[molecule]]. | : '''Chemical Formulae''' show which [[element]]s are in a [[molecule]]. | ||
: The number of each [[element]] in a [[molecule]] is shown with subscript after that [[element]]. | : The number of each [[element]] in a [[molecule]] is shown with subscript after that [[element]]. | ||
+ | : Some '''chemical formulae''' have brackets which indicate that the [[element]]s in the bracket are multiplied by the number after the bracket. | ||
*MgBr<sub>2</sub>: [[Magnesium Bromide]] with 1 [[Magnesium]] [[atom]] and 2 [[Bromine]] [[atom]]s. | *MgBr<sub>2</sub>: [[Magnesium Bromide]] with 1 [[Magnesium]] [[atom]] and 2 [[Bromine]] [[atom]]s. | ||
*CO<sub>2</sub>: [[Carbon Dioxide]] with 1 [[Carbon]] [[atom]] and 2 [[Oxygen]] [[atom]]s. | *CO<sub>2</sub>: [[Carbon Dioxide]] with 1 [[Carbon]] [[atom]] and 2 [[Oxygen]] [[atom]]s. | ||
*Li<sub>2</sub>O: [[Lithium Oxide]] with 2 [[Lithium]] [[atom]]s and 1 [[Oxygen]] [[atom]]. | *Li<sub>2</sub>O: [[Lithium Oxide]] with 2 [[Lithium]] [[atom]]s and 1 [[Oxygen]] [[atom]]. | ||
+ | *Al(OH)<sub>3</sub>: [[Aluminium Hydroxide]] with 1 [[Aluminium]] [[atom]], with 3 lots of OH; 3 [[Oxygen]] [[atom]]s and 3 [[Hydrogen]] [[atom]]s. | ||
+ | *Al<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub>: [[Aluminium Carbonate]] with 2 [[Aluminium]] [[atom]]s, and 3 lots of CO<sub>3</sub>; 3 [[Carbon]] [[atom]]s and 9 [[Oxygen]] [[atom]]s. | ||
Some '''chemical formulae''' are written with the [[element]]s at specific points, not all grouped together, to show where different [[element]]s are [[Chemical Bond|bonded]]. This is called a [[Structural Formula|structural formula]]. | Some '''chemical formulae''' are written with the [[element]]s at specific points, not all grouped together, to show where different [[element]]s are [[Chemical Bond|bonded]]. This is called a [[Structural Formula|structural formula]]. |
Revision as of 18:31, 8 December 2018
Contents
Key Stage 3
Meaning
A Chemical Formula is a simple way to show the number and type of atoms in a chemical.
About Chemical Formulae
- Chemical Formulae show which elements are in a molecule.
- The number of each element in a molecule is shown with a number written just after and lower than the element.
Examples
H2O | CO2 | CH4 | C2H5OH |
Water has 2 Hydrogen atoms and 1 Oxygen atom. | Carbon Dioxide has 1 Carbon atom and 2 Oxygen atoms. | Methane has 1 Carbon atom and 4 Hydrogen atoms. | Ethanol has 2 Carbon atoms, 6 Hydrogen atoms and 1 Oxygen atom. |
Key Stage 4
Meaning
A Chemical Formula is a way to show the numbers of atoms of each element in a chemical.
About Chemical Formulae
- Chemical Formulae show which elements are in a molecule.
- The number of each element in a molecule is shown with subscript after that element.
- Some chemical formulae have brackets which indicate that the elements in the bracket are multiplied by the number after the bracket.
- MgBr2: Magnesium Bromide with 1 Magnesium atom and 2 Bromine atoms.
- CO2: Carbon Dioxide with 1 Carbon atom and 2 Oxygen atoms.
- Li2O: Lithium Oxide with 2 Lithium atoms and 1 Oxygen atom.
- Al(OH)3: Aluminium Hydroxide with 1 Aluminium atom, with 3 lots of OH; 3 Oxygen atoms and 3 Hydrogen atoms.
- Al2(CO3)3: Aluminium Carbonate with 2 Aluminium atoms, and 3 lots of CO3; 3 Carbon atoms and 9 Oxygen atoms.
Some chemical formulae are written with the elements at specific points, not all grouped together, to show where different elements are bonded. This is called a structural formula.
- CH3COOH: Ethanoic Acid with 2 Carbon atoms, 2 Oxygen atoms and 4 Hydrogen atoms. This shows that one Carbon is bonded to three Hydrogen atoms while the other Carbon is double bonded to one Oxygen and has a single bond with an Oxygen, which itself it bonded to a Hydrogen.
- CH3CH2COOH: Propanoic Acid with three Carbon atoms, two Oxygen atoms and 6 Hydrogen atoms.
Examples
HCl | H2SO4 | C3H8O | C3H8O |
Hydrochloric Acid molecules have 1 Hydrogen atom and 1 Chlorine atom. | Sulphuric Acid molecules have 2 Hydrogen atoms, 1 Sulphur atom and 4 Oxygen atoms. | Propanol or Propan-1-ol has 3 Carbon atoms and 8 Hydrogen atoms and 1 Oxygen atom. This has the same chemical formula as Propan-2-ol but a different shape. This may be written with the structural formula CH3CH2CH2OH to show where the OH group is attached. | Isopropyl Alcohol or Propan-2-ol has 3 Carbon atoms and 8 Hydrogen atoms and 1 Oxygen atom. This has the same chemical formula as Propan-1-ol but a different shape. This may be written with the structural formula CH3CHOHCH3 to show where the OH group is attached. |