Iron Age.
Antimony (Sb) is not a mineral but a chemical element, a metalloid placed in the group 15 and period 5 of the periodic table of Mendeleev.
Hafnium is an element not a rock. Hafnium is never found in nature pure form so does not fit into any groups. Hafnium is a chemical element, a metal placed in the group 4 and period 6 of the periodic table of Mendeleev.
Helium is a period 1 element.
He is in period 1.
The element neon is in period 2. Classified as a non-metal. :)
its the 4th period
period 6
He is in period 1.
The first element in the fourth period of the periodic table is potassium (K).
The last element in each period is a noble element. It is non-reactive.
The period of an element is determined by electronic configuration.Period is same as the number of energy levels of the element.
The element in period two group eighteen is neon.