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Question
What is the periodic trend in the variation of valency while going from left to right within a period? Explain your answer with reference to period 2 and period 3.
Explain
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Solution
| 2 | Li 2, 1 |
Be 2, 2 |
B 2, 3 |
C 2, 4 |
N 2, 5 |
O 2, 6 |
F 2, 7 |
Ne 2, 8 |
| 3 | Na 2, 8, 1 |
Mg 2, 8, 2 |
Al 2, 8, 3 |
Si 2, 8, 4 |
P 2, 8, 5 |
S 2, 8, 6 |
Cl 2, 8, 7 |
Ar 2, 8, 8 |
An element's valency changes with time, changing its electronic configuration. These elements have varying numbers of valence electrons. But there are exactly the same amount of shells.
During a period, both the atomic number and the number of valence electrons grow by one at a time as they go from left to right.
Valency changes as one moves from left to right in periods 2 and 3.
| Elements | Li | Be | B | C | N | O | F | Ne |
| Valency | 1 | 2 | 3 | 4 | 3 | 2 | 1 | 0 |
| Elements | Na | Mg | Al | Si | P | S | Cl | Ar |
| Valency | 1 | 2 | 3 | 4 | 3 | 2 | 1 | 0 |
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