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Q15: The half-life of <sup>20</sup>F is 11 s.What
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Q28: Which of the following has not yet
Q41: The frequency and energy of a photon
Q52: A solution with a pH of 14
Q66: The various isotopes of an element all
Q119: When a neutron hits a
Q123: Complete the equation,and state what type
Q125: The complementary angle of the angle of
Q134: The dipole arrow in an S-Se bond