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# Which of the following is NOT true about Cerium (Atomic Number = 58, Electron configuration = [Xe] 4f$^1$5d$^1$6s$^2$)?

(1) Cerium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form cerium hydroxide

(2) Cerium exhibits three oxidation states, +2, +3 and +4 but the +2 state is rare

(3) Cerium cannot be isolated and purified compared to other Lanthanides

(4) There are four isotopes of cerium that occur naturally

(5) Cerium metal reacts with all the halogens except I$_2$

$\begin {array} {1 1}(2) \;and \;(5) \\ (3)\;and (5) \\ (1)\;and\;(4) \\ (2)\;and \;(3) \end {array}$

(3) Cerium cannot be isolated and purified compared to other Lanthanides
$\quad$ The two oxidation states of cerium differ enormously in basicity: cerium(III) is a strong base, comparable to the other trivalent lanthanides, but cerium(IV) is weak. This difference has always allowed cerium to be by far the most readily isolated and purified of all the lanthanides, otherwise a notoriously difficult group of elements to separate.
(5) Cerium metal reacts with all the halogens except I$_2$
$\quad$ Cerium reacts with all halogens: 2Ce (s) + 3I$_2$ (g) $\rightarrow$ 2 CeI$_3$ (s). (Note: This is yellow, while the rest of the halides are white).