Question

write a brief description about Mendeleev periodic table and Modern Periodic Table after going through the chapter periodic classification of elements ​

Answer 1

★ $\large\underline\color{red}{\sf Mendevleev's \: Periodic \: Table }$

$\bullet$ The physical and chemical properties of element are the periodic function of their atomic weight.

$\bullet$ It was based on atomic weight

$\bullet$ 63 elements were known, noble gases were not discovered

$\bullet$ He was the first scientist to classify the elements in a systematic manner i.e. in horizontal rows and vertical columns.

$\bullet$ Horizontal rows were called perioids and there were 7 periods

$\bullet$ Vertical columns are called groups and there were 8 groups

$\bullet$ Each group upto VII was divided into A and B subgroups. 'A' sub group elements were called normal elements and 'B' sub group elements were called transition elements

$\bullet$ The VIII group consisted of 9 elements in three row ( Transition metal group)

$\bullet$ The elements belonging to same group exhibit similar properties.

★ $\large\underline\color{red}{\sf Modern \: Periodic \: Table }$

$\bullet$ It was Proposed by Moseley

$\bullet$ The physical and chemical properties of elements are the Periodic function of their atomic number

$\bullet$ Modern Periodic table is based on atomic number

$\bullet$ Moseley did an experiment in which he bombarded high speed electrons on different metal surfaces and obtained X-ray

He found that ${\sf \sqrt{v}\:\:\propto\:\:Z}$

where v = frequency of X-ray

Z = atomic number

$\bullet$ 9 vertical columns called groups

$\bullet$ I to VIII + 0 group of inert gas

$\bullet$ Inert gases were introduced in Periodic table by Ramsay

$\bullet$ 7 horizontal rows called periods.

Answer 2

1. Explanation:properties of elements are periodic function of their atomic mass it was on base atomic weight
2. he discovered total 63 element
3. noble gas was not discovered at that time
4. he divide the periodic table into two subgroup a and b
5. he made 7 horizontal row called period
6. made 8 vertical column called groups
7. the element belonging to same group have similar properties
8. he corrected some doubtful atomic weight of element
9. example indium 76 after correction 113
10. he left some vacant space in his periodic table on the basis of the periodic properties of other element present in same group
11. name this missing element as a eka boron eka aluminium and eka silicon
12. after correction eka boron as scandium eka aluminium as gallium and eka silicon as germanium