Zirconium (Zr)
Element 40 · Transition metal · Solid at 25 °C · Group 4, Period 5
Zirconium barely absorbs neutrons, making it the standard cladding for nuclear fuel rods. Its oxide becomes cubic zirconia, the well-known diamond substitute.
On the periodic table, zirconium sits in group 4 in period 5. It is one of 38 elements classified as a transition metal, and at room temperature (25 °C) it is a solid.
Transition metals occupy the wide d-block in the middle of the table. As a family they are hard, dense, high-melting metals that conduct heat and electricity well. Their partly filled d-orbitals let many of them take several oxidation states, form vividly colored compounds, and act as catalysts — which is why so much of industry, and so much of biology, runs on this block.
Properties of zirconium
| Atomic number (Z) | 40 |
|---|---|
| Symbol | Zr |
| Atomic mass | 91.224 |
| Category | Transition metal |
| Group | 4 |
| Period | 5 |
| Block | d-block |
| Metal / nonmetal | Metal |
| State at 25 °C | Solid |
| Electron configuration | [Kr] 4d2 5s2 |
| Electronegativity (Pauling) | 1.33 |
| Melting point | 1,855 °C (2,128.15 K / 3,371 °F) |
| Boiling point | 4,409 °C (4,682.15 K / 7,968.2 °F) |
| Density | 6.52 g/cm³ |
Position in the periodic table
Zirconium shares group 4 with Titanium (Ti), Hafnium (Hf), Rutherfordium (Rf). 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
Zirconium melts at 1,855 °C (2,128.15 K / 3,371 °F) and boils at 4,409 °C (4,682.15 K / 7,968.2 °F), giving it a liquid range of about 2,554 °C at standard pressure.
Its density is 6.52 g/cm³.
See also: the interactive periodic table, how to read the periodic table, periodic trends.