84 Po

Polonium (Po)

Element 84 · Post-transition metal · Solid at 25 °C · Group 16, Period 6

Polonium was discovered by Marie and Pierre Curie in 1898 and named for Marie's homeland, Poland. It is intensely radioactive.

On the periodic table, polonium sits in group 16 — the chalcogens (oxygen group) — in period 6. It is one of 12 elements classified as a post-transition metal, and at room temperature (25 °C) it is a solid.

The post-transition metals sit between the transition metals and the metalloids. They are genuine metals — shiny and conductive — but softer, weaker, and lower-melting than the d-block metals, and their chemistry has more covalent character. Everyday examples from this family include aluminium foil, tin cans, and lead batteries.

Properties of polonium

Properties of Polonium
Atomic number (Z)	84
Symbol	Po
Atomic mass	(209) (mass number of the most stable isotope; this element has no standard atomic weight)
Category	Post-transition metal
Group	16
Period	6
Block	p-block
Metal / nonmetal	Metal
State at 25 °C	Solid
Electron configuration	[Xe] 4f14 5d10 6s2 6p4
Electronegativity (Pauling)	2
Melting point	254 °C (527.15 K / 489.2 °F)
Boiling point	962 °C (1,235.15 K / 1,763.6 °F)
Density	9.2 g/cm³

Position in the periodic table

Polonium shares group 16 — the chalcogens (oxygen group) with Oxygen (O), Sulfur (S), Selenium (Se), Tellurium (Te), Livermorium (Lv). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.

Physical properties

Polonium melts at 254 °C (527.15 K / 489.2 °F) and boils at 962 °C (1,235.15 K / 1,763.6 °F), giving it a liquid range of about 708 °C at standard pressure.

Its density is 9.2 g/cm³.

Data notes

The atomic mass is shown in parentheses because this element has no standard atomic weight; the number given is the mass number of its most stable known isotope.