Symbols, Formulae and Equations · 8 min read
Chemical symbols and valency
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Introduction to chemical language
In Chemistry, we do not write full names like 'Hydrogen' or 'Oxygen' every time. It would be too slow, like writing 'Public Health Control Services' instead of just saying NEPA or PHCN. Instead, we use short codes called symbols.
Chemical symbols represent elements. Each element has a unique symbol, usually one or two letters. The first letter is always a capital letter, and the second is always a small letter. For example, Calcium is Ca, not CA or ca.
Think of a symbol as a nickname for an element that everyone in the world understands.
How symbols are formed
1. The first letter of the English name: Hydrogen (H), Carbon (C), Oxygen (O).
2. The first two letters of the English name: Calcium (Ca), Aluminum (Al), Magnesium (Mg).
3. Symbols from Latin names: Sodium comes from Natrium (Na), Iron from Ferrum (Fe), and Potassium from Kalium (K).
Understanding valency
Valency is like the 'hands' an atom uses to hold others. Just as a person has two hands to hold things, different atoms have different capacities to join with others. If an atom has a valency of 1, it has one 'hand' to hold another atom.
Simply put, valency tells us how many bonds an atom can form to be stable.
Valency and the periodic table
For the first 20 elements, you can find the valency by looking at the outer electrons. Elements in Group 1 (like Na) have a valency of 1. Group 2 (like Mg) have a valency of 2. Group 7 elements (like Cl) also have a valency of 1 because they need only one more electron to be full.
Radicals and their valencies
Sometimes, a group of atoms stays together and acts as one unit. We call these radicals. Common examples include the Hydroxyl radical (OH^-) with a valency of 1, and the Sulfate radical (SO42-) with a valency of 2.
Worked example of finding valency
Question: What is the valency of Aluminum (Al) if its atomic number is 13?
1. Write the electronic configuration: 2, 8, 3.
2. Look at the outermost shell: It has 3 electrons.
3. Determine the number of electrons to lose or gain: It is easier to lose 3 electrons than to gain 5.
4. Conclusion: The valency of Aluminum is 3.
Key points
- •Symbols are one or two-letter codes for elements.
- •Symbols can come from English or Latin names.
- •Valency is the combining power of an atom.
- •Valency depends on the electrons in the outer shell.
- •Radicals are groups of atoms that act as a single unit with a specific valency.