SECTION D
Answer the following 9. nos. 35 to 39 in detail withi
limit of 90 to 120 words as directed : [4 marks
Chapter 4
1. Explain Rutherford's experiment in brief. State observation
of this experiment and give its results.
2. Write a short note about isotopes and write two uses also
3. Which scientist suggested the distribution of electrons in
various orbits of an atom ? State the rules for writing the
number of electrons in different energy levels.
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Answers
Answer:
Explain Rutherford's experiment in brief. State observation
Ernest Rutherford's experiment of shooting alpha particles through a thin sheet of gold, and discovering that some were deflected, proved that an atom is actually a small dense nucleus surrounded by orbiting electrons. The observations made by Rutherford led him to conclude that: A major fraction of the α-particles bombarded towards the gold sheet passed through it without any deflection, and hence most of the space in an atom is empty
Write a short note about isotopes and write two uses also
Isotopes are samples of an element with different numbers of neutrons in their atoms. The number of protons for different isotopes of an element does not change. Not all isotopes are radioactive. Stable isotopes either never decay or else decay very slowly. Uses - In medicine, for example, cobalt-60 is extensively employed as a radiation source to arrest the development of cancer. Other radioactive isotopes are used as tracers for diagnostic purposes as well as in research on metabolic processes.
Which scientist suggested the distribution of electrons in various orbits of an atom ? State the rules for writing the number of electrons in different energy levels.
Neils Bohr suggested the distribution of electrons in various orbits of an atom.
Rule 1: The maximum number of electrons present in a particular shell is calculated by the formula 2n2, where “n” represents the shell number. For instance, K shell is the first shell and it can hold up to 2(1)2 = 2 electrons. Similarly, L shell is the second shell and it can hold up to 2(2)2 = 8 electrons. This formula helps to calculate the maximum number of electrons that an orbit can accommodate.
Rule 2: The maximum capacity to hold electrons in the outermost shell is 8.
Rule 3: The electrons will fill the inner shells before the outer shells. First electrons will fill the K-shell and then L shell and so on. Thus, electronic configuration of elements follows an ascending order.