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प्रश्न
How did the early chemists classify elements?
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उत्तर
Early chemists classified the elements on the bases of their properties, nature, character, valency, and whether they were metals or non-metals.
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संबंधित प्रश्न
An element P (atomic number 20) reacts with an element Q (atomic number 17) to form a compound. Answer the following questions giving reason:
Write the position of P and Q in the Modern Periodic Table and the molecular formula of the compound formed when P reacts with Q.
Rewrite the following statement after correction, if necessary:
Isotopes are the elements of the same group.
The following diagram shows a part of the periodic table containing first three periods in which five elements have been represented by the letters a, b, c, d and e (which are not their chemical symbols):
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1 18 a 2 13 14 15 16 17 b c d e
(i) Select the letter which represents an alkali metal.
(ii) Select the letter which represents a nobles gas.
(iii) Select the letter which represents a halogen.
(iv) What type of bond is formed between a and e?
(v) What type of bond is formed between d and e?
Find the neutral atom in the periodic table which has the same number of electrons as K+ and Cl−. What is this number?
Rearrange the columns 2 and 3 so as to match with the column 1.
| Column 1 | Column 2 | Column 3 |
| i. Triad ii. Octave iii. Atomic number iv. Period v. Nucleus vi. Electron |
a. Lightest and negatively charged particle in all the atoms b. Concentrated mass and positive charge c. Average of the first and the third atomic mass d. Properties of the eighth element similar to the first e. Positive charge on the nucleus f. Sequential change in molecular formulae |
1.Mendeleev
2. Thomson
3. Newlands
4. Rutherford
5. Dobereiner
. Moseley
|
Give a reason why elements need to be properly classified.
Classify the following elements into Metals and Nonmetals.
S, Mg, Al, P, N, Na.
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 ______
An element X of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in presence of the catalyst to form a compound, ammonia which has a characteristic pungent smell.
- Identify the element X. How many valence electrons does it have?
- Draw the electron dot structure of the diatomic molecule of X. What type of bond is formed in it?
- Draw the electron dot structure for ammonia and what type of bond is formed in it?
