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प्रश्न
What are orbits or shells ?
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उत्तर
The fixed circular paths along which electrons revolve round the nucleus.
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संबंधित प्रश्न
TRUE \ FALSE
Elements combine in definite proportions to form compounds.
What is the maximum number of electrons present in:
1. first shell
2. second shell
3. third shell and
4. fourth shell
Give two examples for each of ionic and covalent bond.
How did Neils Bohr visualise the atom ?
An atom has 13 protons and 14 neutrons.
What is the atomic mass of the atom ?
Fill in the blank
If an atom gains an electron, it is called an _______
Fill in the blank
An excess of electrons produces a ________ charge.
What is the usual symbol for (a) and electron (b) a proton, and (c) a neutron?
An atom of an element X may be written as `""_9^4"X"`
(a) What does the figure 9 indicate?
(b) What does the figure 4 indicate?
(c) What is the number of protons in atom X?
(d) What is the number of neutrons in atom X?
(e) What is the number of electrons in atom X?
(f) How many electrons are there in the outermost shell of an atom of element X?
(g) Write the symbol of ion formed by an atom of element X.
For the symbols H, D and T, write the subatomic particles (protons, neutrons and electrons) found in each one of them.
How many atoms are there in exactly 12 g of carbon-12 element ? (C = 12 u)
Which has more atoms, 50 g of aluminium or 50 g of iron ? Illustrate your answer with the help of calculations.
(Atomic masses : Al = 27 u ; Fe = 25 u)
Match the pairs.
| Group 'A' | Group 'B' |
| a. Proton | i. Negatively charged |
| b. Electron | ii. Neutral |
| c. Neutron | iii. Positively charged |
Elements X and Y have 1 and 7 electrons in their outermost shell respectively.
What will be the charge present of the molecule XY after chemical combination?
Rewrite the given sentence in correct form.
Elements contain two or more kind of atoms and compounds contain only one kind of atom.
Define the term ions or radicals.
Atoms of different elements having ______ mass numbers, but ______ atomic numbers are called isobars.
Which of the following has maximum number of atoms?
The most abundant type of atom is the universe is ______.
