First slide

Modern approach of classification of elements

Question

Which of the following statement is/are correct?

Moderate

A

In the lanthanide series the electrons occupy 4f-orbtals in preference to 5d the and 6p-orbitals.
B

Zero group was not present in the periodic table when Mendeleev presented it.
C

Law of octave was presented by Newland.
D

Cuprous compounds are coloured while cupric compounds are colourless

Solution

Statement (a) is wrong.
$\begin{array}{l} Cu (Z = 29), 3 d^{10}, 4 s^{1} \\ {Cu}^{\oplus} (cuprous) = 3 d^{10} 4 s^{0} \\ {Cu}^{2 +} (cupric) = 3 d^{9} 4 s^{0} \end{array}$
(one unpaired electron and hence is coloured)

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