Tag: classification of elements- the periodic table

Questions Related to classification of elements- the periodic table

Classification of periodic table based on atomic number is given by:

chemistry classification of elements- the periodic table introduction to periodic table necessity of classification need for classification

  1. Mendeleev's

  2. Mosley

  3. Both A and B

  4. None of these

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Correct Option: B
Explanation:

Henry Moseley found a relationship between the X-ray wavelength of an element and its atomic number. Moseley's discovery showed that atomic numbers were in fact based upon experimental measurements.

The first attempt to classify elements systemically was made by :

chemistry classification of elements- the periodic table development of the modern periodic table into the history mendeleef's periodic table

  1. Mendeleev

  2. Newland

  3. Lother Meyer

  4. Dobereiner

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Correct Option: D
Explanation:

The first attempt to classify elements systemically was made by Dobereiner.
The triads of elements that showed similar chemical properties.
Other properties of the elements followed trends in which the value of the middle element of the triad was in between those of the end members.

The arrangement of elements in a group of three is known as Law of Triads.

chemistry classification of elements- the periodic table development of the modern periodic table into the history mendeleef's periodic table

  1. True

  2. False

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Correct Option: A

The atomic masses of Li and K are 7 and 39, respectively. According to law of triads the atomic mass of Na will be:

chemistry classification of elements- the periodic table development of the modern periodic table into the history mendeleef's periodic table

  1. 23

  2. 32

  3. 46

  4. 64

Show answer
Correct Option: A
Explanation:
Dobereiner arranged the elements in increasing order of atomic masses. He found that the atomic mass of the middle element was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad when they are arranged in their increasing order of atomic mass.

So Li=7,K=39

Atomic mass of Na = $\dfrac{7+39}{2}=\dfrac{46}{2}=23$