How many chemical elements have only seven letters in their name?
I count 23 : Lithium, Silicon, Calcium, Gallium, Krypton, Arsenic , Bromine, Yttrium, Niobium , Rhodium, Cadmium, Caesium, Terbium, Holmium, Thulium, Hafnium, Rhenium, Mercury, Thorium, Fermium,...