Question

The number of elements in 5th and 6th period of periodic table are respectively:
$\text{A}\text{. 8,18}$
$\text{B}\text{. 18,18}$
$\text{C}\text{. 18,32}$
$\text{D}\text{. 18,28}$

Answer 1

Hint: In a periodic table elements are arranged as per their increasing order of their atomic number and electron configuration, and recurring chemical properties.

Complete step-by-step answer:
Currently there are 115 known elements. The elements are graded according to their properties, into different periods and groups. It was very difficult to research the properties of elements separately in an earlier period of time and classify them into classes, based on their existence.
All elements in a row have similar numbers of shells of electrons. Every next element has one more proton at one time and is less metallic than its previous element. Arranged in this way, groups of elements have identical chemical and physical properties in the same column, representing the periodic law.
In the s-block and p-block of the periodic table, elements usually do not show patterns and differences in their properties within the same time span which is more important are vertical patterns down groups. However, patterns over time are becoming important in the d-block, and the f-block elements display a high degree of similarity over time.
The fifth cycle is composed of 18 elements, beginning with rubidium and ending with xenon. The elements in period 5 fill their electrons in their s shells first, then their 4d and 5p shells in the mentioned order. However, there are few exceptions, like as rhodium
The sixth cycle consists of 2 elements from s-block, 10 from d-block, 14 from f-block and 6 from p-block, i.e. a total of 32 elements.
Hence our answer is that the number of elements in the 5th and 6th period of periodic table respectively are 18 and 32 and our correct option is Option C.

Note: It is very important to remember the properties of s-block, d-block, f-block and p-block. elements. Also, we must remember the process by which the electrons get filled into their various shells. The number of electrons in each shell is based on the rule $2(n^2)$. Where $n$ is the number of $n^{th}$ row.