Skip to content 1 Identify the number of electrons in the outermost shell of the following elements:
SA (Short)
2 If a bromine atom is available in the form of, say two isotopes, 3579Br (49.7\%) and 3581Br (50.3\%), calculate the average atomic mass of the bromine atom. [Pg. No. 156]
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3 Write the electronic configuration of the elements having atomic numbers 12, 16 and 18.
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4 Two different atoms have 11 protons each, but one has 12 neutrons, and the other has 13 neutrons.
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5 Choose the correct options and explain the reason for the correct and incorrect options in the context of Ernest Rutherford's gold foil experiment:
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6 Solve this riddle: I am an atom with a mass number of 23 and 11 protons.
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7 What conclusion did Rutherford draw about the position and characteristics of the atom's positively charged part based on the few alpha particles that bounced back or were…
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8 The composition of the nuclei of three atomic species X, Y, and Z are given as follows.
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9 Explain and arrange the following statements in the correct chronological order to show how atomic models have evolved over time.
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10 Electrons move around the nucleus in orbits.
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11 Which of the following statements are correct or incorrect according to the Bohr's atomic model?
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12 Find the following information for the elements shown in the given figure:
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13 Magnesium is essential for many biological processes, including muscle contraction.
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14 Both Rutherford's and Bohr's models have electrons orbiting the nucleus.
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15 An atom 70X has 31 electrons.
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16 Assertion (A): The discovery of subatomic particles helped in understanding the atomic structure.
AR (Assertion & Reason)
17 An atom has 79 protons and a mass number of 197.
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18 Aman was discussing the structure of atom with his classmates.
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19 Complete the given table: Atomic NumberMass NumberNumber of NeutronsNumber of ProtonsNumber of ElectronsName of the Element5-6----14--7Nitrogen-24-12--15-16----10---
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20 In an atom, there are 12 protons and 12 neutrons in the nucleus.
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21 Are atoms the smallest indivisible particles?
VS (Very Small)
22 Why do electrons not fall into the nucleus even though they are attracted to protons in it?
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23 What if an atom had no empty space?
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24 Why did scientists keep modifying atomic models?
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25 Observe the given figure of the gold foil experiment.
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26 Suppose you made up your own 'atom', as Thomson described, using clay for the positive charge and small beads for the electrons spread through it.
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27 Could an orange or a lemon, which also contain seeds inside soft pulp, be a good comparison?
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28 What do you think would happen if α-particles were replaced with negatively charged particles in Rutherford's gold foil experiment?
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29 Why did Thomson conclude that electrons are present in all atoms?
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30 Rutherford found that a few α-particles bounced back sharply.
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