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Po

Polonium

Polonium is a chemical element with the symbol Po and atomic number 84. It has a mass number of 209, sits in period 6 and group 16, and is classified as a post-transition metal.

Properties

SymbolPo
Atomic number84
Mass number209
CategoryPost-transition metal
Group16
Period6
Electron configuration[Xe] 4f14 5d10 6s2 6p4
Outer-shell electrons6

The figure of 209 is a mass number rather than a measured atomic weight, because this element has no stable isotope.

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Group 16

Atomic weights are the IUPAC 2021 standard values, abridged to the conventional five significant figures. Group, period, category and electron configuration are derived from the atomic number rather than stored, so they cannot drift out of step with it.