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प्रश्न
Explain the Atomic number with example.
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उत्तर
- The number of protons present in the nucleus of an atom is called atomic number.
- It is denoted by Z.
- e.g., in `""_20^40Ca,` atomic number = 20
संबंधित प्रश्न
Explain the Mass number with example.
Multiple Choice Questions
If the atomic number of an atom is 17 and mass number is 35 then number of neutron will be
What is variable valency? Name two elements having variable valency and state their valencies.
Fill in the blank of the following statement :
All the mass of an atom is concentrated in a small region of space called the ___________.
Fill in the following blanks in respect of an atom of an element
| No. of protons | No. of neutron | Mass number | Atomic number | No. of electrons | Symbol |
| 11 | 12 | ___________ | ___________ | ___________ | ________ |
An atom of an element has two electrons in the M shell.
What is the (a) atomic number (b) number of protons in this element?
Match the atomic numbers 4,8,10,15 and 19 with the following:
Element which can form trivalent ion
‘Valency is the number of hydrogen atoms which can combine with [or displace] one atom of the element [or radical] forming a compound’. With reference to the above definition of valency, state the valency of chlorine in hydrogen chloride, giving reasons.
Elements X, Y, Z have atomic numbers 6, 9 and 12 respectively. Which one:
- forms anion – negative ion;
- forms cation – positive ion;
- has 4 electrons in the outermost orbit. [Y, Z, X]
State the term for the following:
The amount of substance which contains the same number of units as the number of atoms in carbon-12.
