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प्रश्न
What was the basis of the earliest attempts made for classification and grouping of elements?
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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
Rewrite the following statement after correction, if necessary:
Isotopes are the elements of the same group.
A metal X is in the first group of the periodic table. What will be the formula of its oxide?
Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electron shells but different number of electrons in their outermost shells. It was found that elements A and G combine to form an ionic compound. This ionic compound is added in a small amount to almost all vegetables and dishes during cooking. Oxides of elements A and B are basis in nature while those of elements E and F acidic. The oxide of element D is, however, almost neutral. Based on the above information, answer the following questions:
(a) To which group or period of the periodic table do these elements belong?
(b) What would be the nature of compound formed by a combination of elements B and F?
(c) Which two of these elements could definitely be metals?
(d) Which one of the eight elements is most likely to be found in gaseous state at room temperature?
(e) If the number of electrons in the outermost shell of elements C and G be 3 and 7 respectively, write formula of the compound formed by the combination of C and G.
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.
The non-metal A is an important constituent of our food and most of the fuels around us. A forms two oxides B and C. The oxide B is poisonous whereas oxide C causes global warming.
(a) Identify A, B and C.
(b) To which group of periodic table does A belong?
(c) Name another element which is placed in the same group as A.
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.
Alkaline earth metals have valency 2. This means that their position in the modern periodic table is in ______.
The number of periods and groups in the periodic table are ______
If the distance between two Cl atoms in a Cl2 molecule is 1.98Å, then the radius of the Cl atom is ______.
Which one of the following statements is not correct about the trends in the properties of the elements of a period on going from left to right?
