We will discuss the important periodic trends in some fundamental properties such as valency or oxidation state and chemical reactivity. Let’s see how to explain the periodic trends in chemical properties.
What is periodicity or periodic trends
- Periodicity is the repetition of periodic properties after a regular interval.
- In fact, periodicity is related with electronic configuration.
- Chemical and physical properties depend upon electronic configuration.
- We will discuss here the variation in fundamental properties in the periodic table.
- For example: atomic radii, ionic radii, ionisation energy, electron gain enthalpy and valency.
Periodicity or periodic trend of valence or oxidation state
- Valency is the number of electrons present in the outermost shell.
- It is either equal to number of valence electrons in representative elements or s and p block elements.
- Transition and inner transition elements shows variable valency. There is an involvement of d and f electrons in addition to valence electrons.
Variation of valency along a period
The number of valence electrons increases from 1 to 8 along period.
Variation of valency in the group
All the elements exhibit the same number of valence electrons in a group. Therefore, all the elements exhibit the same valency. Noble gases have zero valency. These elements are chemically inert.
| Group | 1 | 2 | 13 | 14 | 15 | 16 | 17 | 18 |
| Number of Valence electrons | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Valence | 1 | 2 | 3 | 4 | 3, 5 | 2, 6 | 1, 7 | 0, 8 |
Check out the following post on variation of electronegativity here :
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