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Question
Describe the merits of Mendeleev’s periodic table?
Solution
The merits of Mendeleev’s periodic table are followed:
- Atomic masses of some elements were revised so as to give them proper place in the periodic table in accordance with their properties.
For example, the previously determined atomic mass of beryllium, 14.09, was changed to the correct value of 9.4, and beryllium was placed before boron. - Mendeleev kept vacant places in the periodic table for elements not discovered till then. Three of these unknown elements were given the names eka-boron, eka-aluminium and eka-silicon from the known neighbours and their atomic masses were indicated as 44, 68 and 72, respectively. Not only this but their properties were also predicted. Later on these elements were discovered and named as scandium (Sc), gallium (Ga) and germanium (Ge) respectively. The properties of these elements matched well with those predicted by Mendeleev.
- There was no place reserved for noble gases in Mendeleev’s original periodic table. However, when noble gases such as helium, neon and argon were discovered towards the end of nineteenth century, Mendeleev created the ‘ zero’ group without disturbing the original periodic table in which the noble gases were fitted very well.
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The element eka-silicon in Mendeleev’s periodic table is known as ………… in the modern periodic table.
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An element X forms an oxide X2O3. In which group of Mendeleev's periodic table is this element placed?
(a) group II
(b) group III
(c) group V
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Mendeleev predicted the existence of certain elements not known at that time and named two of them as eka-aluminium, and eka-silicon.
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(d) Classify these elements as metals, non-metals or metalloids.
(e) How many valence electrons are present in the atoms of each of these elements?
Why could no fixed position be given to hydrogen in Mendeleev's periodic table?
The correct formula of the oxide of Eka-aluminium element predicted by Mendeleev was:
(a) EaO3
(b) Ea3O2
(c) Ea2O3
(d) EaO
State the merits of Mendeleev's classification of elements.
The elements from the zero group are called _______.
Two elements in the same position : demerit of Newland's octaves : : place for Isotopes : _______
Find the odd one out and give its explanation.
Find the odd one out and give its explanation.
Match the columns.
| Column A | Column B |
| 1) Eka-aluminium | a) Scandium |
| 2) Eka-Silicon | b) Gallium |
| 3) Eka- boron | c) Germanium |
| d) Beryllium |
Match the columns.
| Column A | Column B |
| 1) Triads | a) Mendeleev |
| 2) Octave | b) Dobereiner |
| 3) Atomic number | c) Thomson |
| 4) Atomic mass number | d) Moseley |
| e) Newland |
Write the name.
The family of group 1 elements.
Write the name.
The family of elements having zero valency.
Write scientific reason.
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Match the column:
| Column ‘A’ | Column ‘B’ |
| Alkali metals | (a) Group 18 |
| Halogens | (b) Group 1 |
| Noble gases | (c) Group 17 |
