In the uranyl ion $UO X_{2} X^{2 +}$ , the oxidation state of uranium and the number of $5 f$ electrons remaining on it are respectively

Answer: D

Let x be the oxidation state of U:

x + 2 (- 2) = + 2

, so

x = + 6

. Uranium has six electrons beyond the radon core (

5 f^{3}

6 d^{1}

7 s^{2}

all used), so

U X^{6 +}

has the radon core and zero

5 f

electrons.