Question

Predict block, group and period of Sb.
A) Block-p, Period-5, Group-15
B) Block-p, Period-5, Group-14,
C) Block-s, Period-5, Group-13
D) Block-s, Period-5, Group-11

Answer 1

Sb is the symbol for chemical element Antimony. Its atomic number is 51. Electronic configuration of Sb is $[Kr]4{d^{10}}5{s^2}5{p^3}$. Also, you should know that the value of principal quantum number ($n$) indicates the period number.

Complete answer:
We are asked to predict the block, group and period number of Sb. Sb is the symbol for antimony.
Its electronic configuration is: $[Kr]4{d^{10}}5{s^2}5{p^3}$
Determination of Period:
In the electronic configuration of an element, the principal quantum number ($n$) of the valence electrons represents the period of the element. Here in the case of Sb, valence shell electronic configuration is $5{s^2}5{p^3}$. Here, valence electrons are 5 and they are in the 5th shell. Thus, principal quantum number, $n = 5$ and consequently, period of Sb is 5.
Determination of Block:
There are a total four blocks in the periodic table and these are- s, p, d and f-block. Elements are classified into blocks according to the sub-shell (s, p, d, or f) which is filled by the last electron. Simply means, the sub-shell in which the last electron enters represents the block of the element. In case of Sb, last electron enters in $5p$ orbital and p-subshell. Hence, Sb belongs to p-block.
Determination of Group:
The group number of an element is equal to the sum of number of electrons in the penultimate shell and number of electrons in the valence shell. In case of Sb, there are 10 electrons in the d-subshell ($4{d^{10}}$) which is the penultimate shell. Since, valence shell electronic configuration of Sb is $5{s^2}5{p^3}$, there are 5 electrons in the valence shell. Therefore,
Group number of Sb = no. of electrons in the penultimate shell and valence shell = $10 + 5 = 15$
Hence, the group number of Sb is 15.

Thus, option A is correct.

Note:
For s-block elements, group number is equal to the number of valence electrons whereas for p-block elements, group number is equal to 10 + number of electrons in the valence shell. These 10 electrons belong to the penultimate d-subshell. Also, d-block (comprises a total of 10 groups from group 3 to 14) lies before p-block in the periodic table.