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Chemistry Chapter 3 : Test Yourself
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Chlorine has two isotopes, both of which have:
Reasoning: Isotopes of an element always have the same number of protons (atomic number). In neutral atoms, electrons = protons, so they also have the same number of electrons. They differ only in neutrons, so mass number changes.
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Number of neutrons in 13 27 M are:
Reasoning: Neutrons = Mass number - Atomic number =27-13=14
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Which isotope is commonly used to irradiate cancer cells?
Reasoning: Cobalt-60 emits strong gamma radiation, which is used in cancer radiotherapy to destroy tumor cells.
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M shell has sub-shells:
Reasoning: The M shell (n=3) contains three subshells:● 3s ● 3p ● 3d
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A sub-shell that can accommodate 6 electrons is
Reasoning: ● s → 2 electrons● p → 6 electrons● d → 10 electrons● f → 14 electrons
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₁₁Na has electronic configuration:
Reasoning: Sodium (Na) has 11 electrons. Filling orbitals step by step gives:● 1s² → 2 ● 2s² → 2● 2p⁶ → 6 ● 3s¹ → 1Total =11
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Which of the following statement is not correct about isotopes?
Reasoning: Isotopes have:● Same atomic number● Same protons● Same chemical propertiesBut different physical properties (like mass, density), because neutrons differ.
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Which isotope is used in nuclear reactors?
Reasoning: Uranium-235 is fissile, meaning it can sustain a nuclear chain reaction. U-238 is not easily fissionable under normal reactor conditions.
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