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Question
Define the term Mass number.
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Solution
Mass number refers to the sum of the number of protons and neutrons present in the nucleus of an atom and denoted by A Mass number = Number of protons + Number of neutrons.
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Multiple Choice Questions
The outermost shell of an atom is known as
Define the term Atomic number.
What are the two main parts of which an atom is made of?
Tick the most appropriate answer.
Which of the following scientists observed that cathode rays consists of negatively charged particles?
- John Dalton
- J J Thomson
- James Chadwick
- Democritus
WRITE SHORT ANSWER
What is the number of neutrons present in a potassium atom ?
Draw the electronic configuration of the following elements clearly stating the number of neutrons and protons in their nucleus.
a. Beryllium b. Silicon
c. Chlorine d. Aluminium
e. Nitrogen
Name the negatively charged particle present in the atoms of all the elements.
With reference to the discovery of the structure of an atom, explain in brief – William Crookes experiment for the discovery of cathode rays, followed by – J.J. Thomsons experiment pertaining to the constituents of the cathode rays. State which sub-atomic particle was discovered from his experiment.
What is meant by the term subatomic particles?
