Pa
Protactinium · element 91
Actinide · Solid at room temperature
Protactinium is a chemical element with symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume +4 and even +2 or +3 states.
Key facts
Atomic mass
231.035882 u
how heavy one atom is
Phase (room temp.)
Solid
Density
15.37 g/cm³
how tightly packed it is
Melting point
1841 K (1568 °C)
when solid turns to liquid
Boiling point
4300 K (4027 °C)
when liquid turns to gas
Period
7
its row in the periodic table
Group
3
its column in the periodic table
Block
F-block
the neighbourhood it lives in
Electronegativity
1.5
how strongly it pulls electrons
Electron configuration
[Rn] 5f2 6d1 7s2
where its electrons live
Shells
2 · 8 · 18 · 32 · 20 · 9 · 2
electrons in each layer, inside to out
Discovered by
William Crookes
who found it
Named by
Otto Hahn
who gave it its name
Appearance
bright, silvery metallic luster
what it looks like
Source: Wikipedia