Question

1)Write down IUPAC name and symbol of the following atomic number: 111,105,102,115?
2)Why do Zr and Hf have similar radius?

Answer 1

1)

For the element having an atomic number more than 100, IUPAC fixed some set of rules. According to these rules, the elements are named according to their atomic number.

In this systems each number has certain code name like $1=un$, $2=bi$, $3=tri$, etc.

therefore these elements can be named as follow:

Atomic number	Symbol	IUPAC name
111	Uuu	Unununnium
105	Unp	Unnilpentium
102	Unb	Unnilbium
115	Uup	Ununpentium

2)

Due to the Lanthanoid contraction, $Zr$ and $Hf$ have almost similar atomic radii. The electrons present in the inner shells shield the outer electron from the nuclear charge making them experience a low effective nuclear charge.

The shielding effect exerted by the electron decreasing in the order $s>p>d>f$.

The f-subshell poorly shields the outer electrons from nuclear attraction which results in the most attractive pull of nucleus on the outer electron.