Question #b5bf3

The whole periodic table is divided into four blocks. Groups 1 and 2 are called the s-block, because all the elements in those groups have electronic configurations ending is the s-orbital. For example, in Group 1, lithium has an electronic configuration of `1s^2 2s^1` and Francium has an electronic configuration `[Rn] 7s^1`. In Group 2, Beryllium has electronic configuration `1s^2 2s^2` and Radium has electronic configuration `[Rn] 7s^2`. As you can see, in both these groups, all the elements have electronic configuration such that they end in a s-orbital.

The transition metals, from Group 3 to Group 12, are called the d-block. The elements in these groups have electronic configuration such that they end in the d-orbital. Example:
`Sc` : `1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1`
`Hg` : `[Xe] 5d^10`

The elements from Groups 13 to 18 are called the p-block. They have electronic configuration that end in p-orbital. Example:
`B` : `1s^2 2s^2 2p^1`
`Rn` : `[Xe] 6p^6`
*n.b.: Helium is an exception. Although in group 18, its electronic configuration is `1s^2 2s^2`

In between Group 2 and the transition metals, there is a narrow band of elements in the 6th and 7th periods. They are called the Lanthanides and the Actinides respectively. These elements are the f-block. Their electronic configuration always end in the f-orbital. Example:
`La` : `[Xe] 4f^1`
`Lr` : `[Rn] 4f^14`

Note, I haven't written the full electronic configuration. I've only shown the last part of the configuration for elements with large atomic numbers, because that's the only relevant part in your question. ![http://www.drcruzan.com/Chemistry_PeriodicTable.html]()