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WEEK: 4
TOPIC: VALENCY, OXIDATION NUMBER, IONS AND RADICALS
CONTENT
- Valency of elements
- Oxidation numbers of elements in compounds
- Ions and radicals
PERIOD 1: VALENCY OF ELEMENTS
VALENCY
The valency of an element is the combining power of the element. It is defined as the number of atoms of hydrogen that will combine with or displace one atom of the element in chemical reactions. Some elements have more than one valency. For example.
First twenty elements with their valences show this character.
| Atomic Number | Element | Symbol | Valency |
| 1 | Hydrogen | H | 1 |
| 2 | Helium | He | Nil |
| 3 | Lithium | Li | 2 |
| 4 | Beryllium | Be | 2 |
| 5 | Boron | B | 3 |
| 6 | Carbon | C | 2 or 4 |
| 7 | Nitrogen | N | 3 or 5 |
| 8 | Oxygen | O | 2 |
| 9 | Fluorine | F | 1 |
| 10 | Neon | Ne | Nil |
| 11 | Sodium | Na | 1 |
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