1. The number of each electron in this shell determines how an atom combines with other atoms to form compounds.
2. The number of electrons in an atom's outermost valence shell governs its bonding behavior.
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After the 1st half-life 250 g of the radioactive material will be left.
<span>After the 2nd half-life 125 g of the radioactive material will be left. </span>
<span>After the 3rd half-life 62.5 g of the radioactive material will be left. </span>
<span>Therefore after 60 minutes, 3 half lives would have occurred. </span>
<span>Therefore the half-life = 60 / 3 = 20 minutes when 250 grams of the original material would have remained radioactive. </span>
<span>Therefore the answer is A) About 250 gram of the material decayed in 20 minutes.</span>