Atomic radius is expressed in units

Which element has largest atomic radius?

The number of periods in the long form of periodic table is

The  first period has only _________ elements.

The outermost electronic configuration of alkali metals is

The electronegativity  of  flourine  is

Elements having incompletely filled outermost shell is known as

The law of triads was introduced by

 The element with the lowest first  ionization energy is

Lanthanoids are