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प्रश्न
The basis of the classifications proposed by Dobereiner, Newlands and Mendeleev was ______.
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उत्तर
The basis of the classifications proposed by Dobereiner, Newlands and Mendeleev was atomic masses
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संबंधित प्रश्न
An element Y is in second period and group 16 of the periodic table:
(i) Is it a metal or non-metal?
(ii) What is the number of valence electrons in its atom?
(iii) What is its valency?
(iv) What is the name of the element?
(v) What will be the formula of the compound formed by Y with sodium?
(a) How is possible valency of an element determined from the electronic configuration of its atom ?
(b) Determine the valency of an element X whose atomic number is 15.
What is the need for classification of elements?
Match the following
| 1. | Galvanisation | Noble gas elements |
| 2. | Calcination | Coating with Zn |
| 3. | Redox reaction | Silver-tin amalgam |
| 4. | Dental filling | Alumino thermic process |
| 5. | Group 18 elements | Heating in the absence of air |
An element X from group 2 of the Periodic Table reacts with Y from group 17 to form a compound. Give the formula of the compound.
Name the neutral atom in the Periodic Table which has the same number of electrons as K+ and Cl-.
The element with atomic number 26 will be found in group ______
Which type of elements are poor conductors of heat and electricity?
Arrange the following elements in the order of their decreasing metallic character
Na, Si, Cl, Mg, Al
Complete the following cross word puzzle
Across:
(1) An element with atomic number 12.
(3) Metal used in making cans and member of Group 14.
(4) A lustrous non-metal which has 7 electrons in its outermost shell.
Down:
(2) Highly reactive and soft metal which imparts yellow colour when subjected to flame and is kept in kerosene.
(5) The first element of second Period
(6) An element which is used in making fluorescent bulbs and is second member of Group 18 in the Modern Periodic Table
(7) A radioactive element which is the last member of halogen family.
(8) Metal which is an important constituent of steel and forms rust when exposed to moist air.
(9) The first metalloid in Modern Periodic Table whose fibres are used in making bullet-proof vests
