Chemistry
Give reasons for the following.
Mendeleeff's contributions to the periodic table, laid the foundation for the Modern Periodic Table.
Periodic Table
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Answer
Mendeleeff's contributions to the periodic table, laid the foundation for the Modern Periodic Table because the best classification is the one which puts together those elements which show maximum resemblance and separates the others and Mendeleeff arranged the elements in increasing order of their atomic weights, in horizontal rows called 'periods' and in vertical columns called 'groups'; such that :
- the properties repeat at regular interval
- elements which are similar with respect to their chemical properties are grouped together and have atomic weights of nearly the same value.
- elements in the same group had same 'valency' and similar chemical properties.
- the properties of undiscovered elements left in the vacant gaps was predicted.
- incorrect atomic weights of some of the arranged elements were corrected with the knowledge of the atomic weights of the adjacent elements.
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Related Questions
Select the correct answer from the words in bracket.
- He arranged elements in increasing order of atomic numbers. [Dobereiner/ Moseley / Mendeleeff
- Is a metal in period 2 having electronic configuration 2, 1. [Beryllium / Lithium / Sodium]
- Is a period having elements from atomic no. 11 to 18. [period – 1/2/3]
- The most reactive halogen from group 17. [chlorine/fluorine/bromine]
- Is the group number of the element whose atomic number is 4. [group - 1/group – 2/group – 18]
Fill in the blanks from the words A to F given below.
A: Decreases B: Increases C: Remains same D: Increases by one E: Electropositive F: Electronegative
- Across a period from left to right in the Modern Periodic Table.
No. of electron shells …………… ; No. of valence electrons ……………; Electronegativity ……………; Character of elements changes from …………… to …………… - Down a group in the Modern Periodic Table.
No. of electron shells ……………; No. of valence electrons ……………; Electronegativity ……………; Character of elements changes from …………… to ……………
- Across a period from left to right in the Modern Periodic Table.
Give reasons for the following.
Properties of elements are periodic functions of their atomic numbers and not atomic weights.
Give reasons for the following.
A transition from metallic to non-metallic elements is seen on moving from left to right in a period of the periodic table.