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सी.आई.एस.सी.ई.आयसीएसई ICSE Class 7

Define Number - Chemistry

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प्रश्न

Define: Atomic number

व्याख्या
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उत्तर

Atomic number— Atomic number refers to the number of protons present in an atom. It is denoted by Z.

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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 1.3

संबंधित प्रश्‍न

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

KNO3


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

CaCO3


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

Hydrogen bromide


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 _________


What is the atomicity of the following ?

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

Write the formulae of the following compounds. Also name the elements present in them.

  1. Water
  2. Ammonia
  3. Methane
  4. Sulphur dioxide
  5. Ethanol

In what form does oxygen gas occur in nature ?


In what form do noble gases 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 ?

What are (i) ionic compounds, and (ii) molecular compounds ? Give two examples of each type of compounds.


Molecular compounds are usually formed by the combination between :


Calculate the mass of 3.011 × 1024 atoms of carbon.


Why are the symbols and formulae of substances important?


Give one example of a triatomic molecule


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


State the atomicity of the following:

Oxygen


State the atomicity of the following:

Chlorine


State the atomicity of the following:

Sulphur


State true of false. If false, give the correct statement.

NaCl represents one molecule of sodium chloride.


Classify the following molecules as the molecules of element or compound

1.  
2.  
3.  
4.  

Which of the following is a triatomic molecule?


Two elements sometimes can form more than one compound.


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