CHEMISTRY · Stage 7 · Chapter 2: Elements, Compounds and Mixtures
Chemistry 2.3 Chemical symbols — International IUPAC Notation
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Lesson summary
2.3 Chemical symbols — International IUPAC Notation — Alhussan International Academy — Chemistry (Stages 7–9) notes: Write and read element symbols using international IUPAC conventions and explain why scientists use chemical symbols.Chemical symbol = the one- or two-letter code …
- One-letter symbol
- Two-letter symbol
- Case changes meaning
- First letters
- First and third letters
- Other languages
Section 1 of 6What chemical symbols are
- Chemical symbol = the one- or two-letter code for an element.
- Purpose
- scientists all over the world use the same symbols so they can communicate without confusion.
- All scientists recognise S as sulfur even though it is called belerang in Indonesian, soufre in French and azufre in Spanish.
- IUPAC
- the International Union of Pure and Applied Chemistry controls the system and approves new element names.
Section 2 of 6Rules for writing symbols
- One-letter symbol
- write a capital letter, for example N for nitrogen, not n.
- Two-letter symbol
- write a capital followed by a lowercase letter, for example Mg for magnesium, not mg, MG or mG.
- Case changes meaning
- Co is the element cobalt but CO is carbon monoxide, a compound of carbon and oxygen.
- Examiners award no mark for incorrect case.
Section 3 of 6Where symbols come from
- First letters
- often the first one or two letters of the English name, such as C for carbon, H for hydrogen, O for oxygen and Ne for neon.
- First and third letters
- sometimes the symbol uses these, as in magnesium (Mg) and manganese (Mn).
- Other languages
- some symbols come from Latin or other older names of elements known for centuries.
| Element | Symbol | Origin |
|---|---|---|
| Sodium | Na | natrium |
| Potassium | K | kalium |
| Iron | Fe | ferrum (Latin) |
| Copper | Cu | cuprum |
| Silver | Ag | argentum |
| Gold | Au | aurum |
| Lead | Pb | plumbum |
| Tungsten | W | Wolfram (German) |
- Names from people and places
- americium (Am) and einsteinium (Es) are examples.
Section 4 of 6Symbols in the periodic table
- Most versions of the periodic table give both the names and chemical symbols of the elements in a set order.
- Other languages
- a Chinese periodic table uses the international chemical symbols with Chinese element names.
- Learn the common symbols
- H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Fe, Cu, Zn.
Section 5 of 6Using symbols in formulae
- A symbol stands for one atom of the element, and for the element in general.
- Subscript
- a small number after a symbol shows how many atoms are present, so H2O has two hydrogen atoms and one oxygen atom.
- Counting atoms
- read each capital letter as the start of a new symbol.
- NaCl has one sodium and one chlorine atom.
- CaCO3 has one calcium, one carbon and three oxygen atoms, because the 3 applies only to the O before it.
- Mg(OH)2 has one magnesium, two oxygen and two hydrogen atoms, because the bracket means the 2 applies to both O and H.
- Elements present
- H2SO4 contains hydrogen, sulfur and oxygen.
Section 6 of 6Where symbols are used
- They appear on chemical bottles, in data tables, on the periodic table and in word and symbol equations.
- They are needed for balancing equations and naming compounds.
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