1. The element lithium (Li) exists as two stable isotopes, 6Li (isotopic mass = 6.200 amu) and 7Li (isotopic mass = 7.200 amu). Lithium has an atomic mass of 7.125 amu. What is the percent abundance of 7Li ?(A) 7.5 % (B) 22.3% (C) 90.2% (D) 92.5% (E) none of these

7. Which of the following statements is incorrect? (A) NF3 is a polar molecule. (B) The hybridization of the central atom is sp3 in ? (C) According to the molecular orbital model, the bond order of P2 molecule is three. (D) A material is made from Al, Ga, and As. The mole fraction of each element is 0.25, 0.26, and 0.49, respectively. This material would be an p-type semiconductor. (E) none of these

1. The element lithium (Li) exists as two stable isotopes, 6Li (isotopic mass = 6.200 amu) and 7Li (isotopic mass = 7.200 amu). Lithium has an atomic mass of 7.125 amu. What is the percent abundance of 7Li ?
(A) 7.5 %
(B) 22.3%
(C) 90.2%
(D) 92.5%
(E) none of these

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