Q4 of 23 Page 34

Match the following:

1-f, 2-d, 3-a, 4-e



1. Protons are positively charged particles. It is represented by the symbol “p”. Their mass is slightly less than that of neutron. They remain inside the nucleus.


2. L shell contains 8 electrons. As we know that every shell has 2n2 electrons. For L shell (n=2):


2n2 = 2× 2× 2


8 electrons


3. The mass of an electron is considered to be negligible.


4. Neutrons are the atomic particles which have no charge. They are electrically neutral. Their mass is nearly equal to that of proton. These are present inside the all atoms except hydrogen.


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3

Answer the following:

List the three fundamental particles and their properties.

 3

Answer the following:

Define the terms atomic number and mass number of an element.

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Answer the following:

Define the term ‘isotope’ of an atom with a suitable example.

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Answer the following:

From the symbol 19K40. write the following


1.mass number of Potassium


2. atomic number of Potassium


3. Write the distribution of electrons in an atom of Potassium.