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प्रश्न
What was the basis of the earliest attempts made for classification and grouping of elements?
उत्तर
The basis of the earliest attempts for the classification of elements was the chemical and physical properties observed by the scientists. Some reactions with known elements and compounds were compared.
The atomic weights were used to order them. To group them into groups they tried to observe the periodicity of the properties as the atomic weight increases. Law of triads and then the law of octaves was proposed. Doberneiner, Chancourtois, and Newlands proposed these laws and prepared some tables.
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संबंधित प्रश्न
The element which forms a basis oxide has the atomic number of:
(a) 18
(b) 17
(c) 14
(d) 19
The elements A, B and C belong to groups 1, 14, and 17 respectively of the periodic table.
(a) Which two elements will form a covalent compound?
(b) Which two elements will form an ionic compound?
Write the names and symbols of two very reactive metals belonging to group 1 of the periodic table. Explain by drawing electronic structure, how either one of the two metals reacts with a halogen. With which name is the bond formed between these elements known and what is the class of the compound so formed known? State any four physical properties of such compounds.
An element X (atomic number 17) reacts with an element Y (atomic number 20) to form a compound.
(a) Write the position of these elements in the modern periodic table.
(b) Write the formula of the compound formed.
Justify your answer in each case.
The basis of the classifications proposed by Dobereiner, Newlands and Mendeleev was ______.
Which of the following have inert gases 2 electrons in the outermost shell.
Moseley’s periodic table is based on atomic mass.
Identify the bond between H and F in the HF molecules.
Consider the following elements 20Ca, 8Or 18Ar, 16S, 4Be, 2He
Which of the above elements would you expect to be in group 16 of the Periodic Table?
Complete the following table:
| Symbol | Atomic No | Electronic Configuration | |
| 1. | He | 2 | ______ |
| 2. | Ne | ______ | 2,8 |
| 3. | Ar | ______ | 2, 8,8 |
| 4. | Na | 11 | ______ |
