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सी.आई.एस.सी.ई.आयसीएसई ICSE Class 7

Define : Atomic Number

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प्रश्न

 Define: Atomic number

व्याख्या
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उत्तर

Atomic number : Number of protons present in the nucleus of an atom.

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पाठ 4: Atoms, Molecules and Radicals - Additional questions

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सेलिना Concise Chemistry [English] Class 7 ICSE
पाठ 4 Atoms, Molecules and Radicals
Additional questions | Q 21.2

संबंधित प्रश्‍न

Write down the name of a compound represented by the following formula:

Al2(SO4)3


Write down the name of a compound represented by the following formula:

CaCl2


Write down the name of a compound represented by the following formula:

KNO3


Give the name of the element present in the following compound:

Quick lime


Give the name of the element present in the following compound: 

Potassium sulphate


State the term.

The number of atoms present in a molecule of an element _________


Define: Atomic number


Define: Atomic weight :


What is the atomicity of the following ?

  1. Oxygen
  2. Ozone
  3. Neon
  4. Sulphur
  5. Phosphorus
  6. Sodium

In what form does oxygen gas occur in nature ?


What is the difference between the molecule of an element and the molecule of a compound ? Give one
example of each.


One of the forms of a naturally occurring solid compound P is usually used for making the floors of houses. On adding a few drops of dilute hydrochloric acid to P, brisk effervescence are produced. When 50 g of reactant P was heated strongly, than 22 g of a gas Q and 28 g of a solid R were produced as products. Gas Q is the same which produced brisk effervescence on adding dilute HCl to P. Gas Q is said to cause global warming whereas solid R is used for white-washing.

  1. What is (i) solid P (ii) gas Q, and (iii) solid R.
  2. What is the total mass of Q and R obtained from 50 g of P ?
  3. How does the total mass of Q and R formed compare with the mass of P taken ?
  4. What conclusion do you get from the comparison of masses of products and reactant ?
  5. Which law of chemical combination is illustrated by the example given in this problem ?

Work out the formula for magnesium hydrogencarbonate.


An element X forms the following compounds with hydrogen, carbon and oxygen :

H2X, CX2, XO2, XO3

State the three valencies of element X which are illustrated by these compounds.


Why are the symbols and formulae of substances important?


Give one example of a triatomic molecule


Give one example of a polyatomic molecule.


State the main points of the contradiction of Dalton’s atomic theory by the Modern Atomic Theory.


Give a reason why –

Helium is considered monoatomic, but hydrogen a diatomic molecule.


State the atomicity of the following:

Oxygen


State the atomicity of the following:

Chlorine


Which of the following is a short and scientific way of representing one molecule of an element or compound?


The Atomicity of phosphorous is ______


Define: Atomicity.


Give any two examples for heterodiatomic molecules.


Which of the following contains maximum number of molecules?


Write any two classifications of a molecule.


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