Explanation
A neutral sodium atom is likely to achieve an octet in its outermost shell by losing its one valence electron. The cation produced in this way is Na+, having electronic configuration [Ne] 3s0 which means there is no unpaired electron.
Hence, Na is diamagnetic in its existing ion form.
A reduction in atomic/ionic size with increase in atomic number is a characteristic of lanthanoids. Hence, the ionic radius of Lu3+ will be smaller than the ionic radius of La3+ It will be less than 1.06 Å. Hence, the option C, 0.85 Å is the correct answer.
Actinoids are element 89 to 103 and fill their 5f shell. They are typical metals and radioactive also. Eg−Th,U,Pu.
U(z=92)→5f36d17s2
Np(z=93)→5f46d17s2
Pu(z=94)→5f66d07s2
Am(z=95)→5f76d∘7s2
So, U and Np have one electron in 6d orbital.
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