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A sample of 32P initially shows activity of one Curie. After 303 days, the activity falls to 1.5 × 104 dps. What is the half-life of 32P?
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The half-life of radon is 3.82 d. By what time would 99.9% of radon will be decayed?
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A sample of old wood shows 7.0 dps/g. If the fresh sample of tree shows 16.0 dps/g, how old is the given sample of wood? (Half-life of 14C is 5730 y)
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Explain the following.
The ionic radii of FΘ and Na⊕ are 133 and 98 pm, respectively.
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Explain the following.
The atomic radii of Cl, I, and Br are 99, 133, and 114 pm, respectively.
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Explain the following.
13Al is a metal, 14Si is a metalloid and 15P is a nonmetal.
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Explain the following.
Cu forms coloured salts while Zn forms colourless salts.
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Answer the following.
Ionization enthalpy of Li is 520 kJ mol-1 while that of F is 1681 kJ mol-1. Explain.
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Answer the following.
Explain the screening effect with a suitable example.
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Answer the following.
Why the elements belonging to the same group do have similar chemical properties?
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Answer the following.
Why the second ionization enthalpy is greater than the first ionization enthalpy?
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Answer the following.
Explain electronegativity and electron gain enthalpy. Which of the two can be measured experimentally?
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Choose the correct option.
Consider the elements B, Al, Mg, and K predict the correct order of metallic character:
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Choose the correct option.
The lanthanides are placed in the periodic table at
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If the valence shell electronic configuration is ns2np5, the element will belong to
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Which of the following pairs is isoelectronic?
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Answer the following question.
For the following pair, indicate which of the two species is of large size:
Fe2+ or Fe3+
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Answer the following question.
For the following pair, indicate which of the two species is of large size:
Mg2+ or Ca2+
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Answer the following question.
Select the smaller ion form the following pair:
K+, Li+
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Answer the following question.
Select the smaller ion form the following pair:
N3–, F–
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