Predict the group number and block to which the given elements belong.
`A(Z=9),B(Z=20) and C(Z=29)`

Explanation

A. `1 s^(2), 2s^(2),2p^(5)(Z=9)`
The last electron is in the `2p`-orbital, therefore it belongs to `p`-block elements.
`:.` Group number `=10+7=17`
Period of the element `=2nd [{:("Number of the "),("pricipal quantum"),("valence shell"):}]`
Hence `A="group" 17` and 2nd period.
B. `1s^(2),2s^(2)2p^(6),3s^(2)3p^(6),4s^(2)(Z=20)`
The last electron is in the `4s`-orbital, therefore it belongs to `s`-block elements.
`:.` Group number `=2` ( Number of electrons in the valence shell)
Period`= 4th`( Number of the principal quantum number of the valence shell)
C. `1s^(2),2s^(2)2p^(6),3s^(2)p^(6),4s^(1),3d^(10)(Z=29)`
The last electron is in the `3d`-orbital, therefore it belongs to `d`-block elements.
`:.` Group number `=11th [{:("Number of electrons in"),("the penultimate shell"),("shell" (i.e. "in" 4s)=10+1),(=11):}]`
Period`=4 th` ( Number of the principle quantum number of the valence shell)
D. `=1s^(2),2s^(2)2p^(6),3s^(2)3p^(6)3s^(10),4s^(2)4p^(6)(Z=36)`
The last electron is in the `4`-p orbital ,therefore it belongs to `p`-block elements.
`:.` Group number `=10+8=18`
Period `=4 th` ( Number of the principle quantum number of the valence shell)
E. `=1s^(2),2s^(2)2p^(6),3s^(2)3p^(6)3d^(10),4s^(2)4p^(6)4d^(10),5s^(2)5p^(6),6s^(2),4f^(2)(Z=58)`
The last electron is in the `4f`-orbital, therefore it belongs to `f`-block elements.
Note: The filling of `4f`-orbitals occurs only when one electron has already entered `5d`-orbital. Therefore, `E` belongs to `f`-blocks elements and not to `d`-block elements.
Since it belongs to lanthanides series, therefore as such it does not have any group number
Note: But all lanthanides and actinides belong to group `3` (or III`B`).
However, its period `= 6 th [{:("Number of hte principal"),("quantum number of"),("the valence shell"):}]`