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प्रश्न
What is variable valency? Name two elements having variable valency and state their valencies.
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उत्तर
Variable valency: Some elements exhibit more than one valency. They are said to have variable valency, e.g. Iron, copper, tin, lead.
Iron Fe Fe2+ or Fe3+
Copper cu cu+ or cu2+
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संबंधित प्रश्न
What are the atomic numbers of elements whose outermost electrons is represented by 2p3.
Multiple Choice Questions
If the atomic number of an atom is 17 and mass number is 35 then number of neutron will be
Name the particles which actually determine the mass of an atom.
What is meant by the 'atomic number of an element'?
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 |
The diagram represents an isotope of hydrogen [H]. Answer the following:
Atomic no. = 1
Mass no. = 1
If an isotope of ‘H’ has mass no. = 2, how many electrons does it have.
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]
If M is the atomic mass and A is the mass number, then packing fraction is given by ______.
In which one of the following, the number of protons is greater than the number of neutrons but number of protons is less than the number of electrons?
A group of elements in the periodic table is given below (Boron is the first member of the group and Thallium is the last).
Boron, Aluminium, Gallium, Indium, Thallium
Answer the following question in relation to the above group of elements:
The atomic number of boron is 5. Write the chemical formula of the compound formed when boron reacts with chlorine.
