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सी.आई.एस.सी.ई.आयसीएसई ICSE Class 7

Define : Atomic Number - Chemistry

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प्रश्न

 Define: Atomic number

व्याख्या

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:

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: 

Baking powder


Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.


Define: Mass number : 


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

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.


An element A forms an oxide A2O5.

What is the valency of element A ?


Give one example of a triatomic molecule


Give a reason why –

Helium is considered monoatomic, but hydrogen a diatomic molecule.


Give a reason why –

Ozone is considered triatomic, but phosphorus a tetratomic molecule.


State the atomicity of the following:

Neon


State the atomicity of the following:

Oxygen


If a molecule is made of similar kinds of atoms, then it is called ______ atomic molecule.


The Atomicity of phosphorous is ______


Derive the relationship between Relative molecular mass and Vapour density.


Which of the following contains maximum number of molecules?


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