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प्रश्न
State the main postulates of Dalton’s atomic theory.
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उत्तर
- Matter consists of small indivisible particles called atoms, i.e., an atom is the basic unit of matter.
- Atoms of the same element are alike in all respects, i.e., atoms of hydrogen have the same properties, such as mass and density, and atoms of oxygen are alike in all respects.
- Atoms of different elements are different from each other. i.e., atoms of hydrogen are different from atoms of oxygen.
- An atom can neither be created nor destroyed.
- Atoms combine with other atoms in a simple whole-number ratio, forming compounds or molecules.
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संबंधित प्रश्न
What are the atomic numbers of elements whose outermost electrons is represented by 3p5?
The atomic number and the mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement.
Fill in the blank of the following statement :
All the mass of an atom is concentrated in a small region of space called the ___________.
The atomic number and mass number of sodium are 11 and 23 respectively. What information is conveyed by this statement?
Match the statements in List I with the correct answer from List II.
| List I | List II |
| 1. Mass number of an atom is the number of protons and | A: Electron |
| 2. The sub-atomic particle with a negligible mass. | B: Argon |
| 3. An atom having stable electronic configuration. | C: Nitrogen |
| 4. A molecule formed by sharing of electrons [covalency] | D: Sodium |
| 5. A metallic atom having unstable electronic configuration. | E: Neutrons |
An element ‘A’ has mass number 23 and atomic number 11. State the –
- no. of neutrons in its shell,
- electronic configuration of the element ‘A’.
Complete the following table.
| Atomic Number | Mass Number | Number of Neutrons | Number of Protons | Number of Electrons | Name of the Element |
| 9 | ______ | 10 | ______ | ______ | ______ |
| 16 | ______ | 16 | ______ | ______ | ______ |
| ______ | 24 | ______ | ______ | 12 | Magnesium |
| ______ | 2 | ______ | 1 | ______ | ______ |
| ______ | 1 | 0 | 1 | 1 | ______ |
The ratio of the radii of hydrogen atom and its nucleus is ~ 105. Assuming the atom and the nucleus to be spherical,
- what will be the ratio of their sizes?
- If atom is represented by planet earth ‘Re ’ = 6.4 ×106 m, estimate the size of the nucleus.
Every atom has an equal number of protons and electrons. The nature of the atom is ______.
Match the following:
| Column A | Column B | ||
| 1. | K shell | a. | 8 |
| 2. | L shell | b. | 32 |
| 3. | M shell | c. | 2 |
| 4. | N shell | d. | 18 |
