Nickel vs Cobalt
Both are transition metals, so they share the same broad chemistry.
The differences in plain English
- They share period 4, the same row, so their outer electrons are in the same shell but they differ in how many there are: Nickel has 2, Cobalt has 2.
- Both are solids at room temperature.
- Nickel is denser, only slightly more than Cobalt (8.908 against 8.9 g/cm³).
- Cobalt melts at 1495 °C, Nickel at 1455 °C.
- An atom of Cobalt is only slightly heavier than an atom of Nickel (58.93 u against 58.69 u).
- Nickel pulls electrons more strongly in a bond (electronegativity 1.91 against 1.88).
Side by side
| Nickel | Cobalt | |
|---|---|---|
| Atomic number | 28 | 27 |
| Symbol | Ni | Co |
| Family | Transition metal | Transition metal |
| Group / period | 10 / 4 | 9 / 4 |
| State at room temperature | Solid | Solid |
| Atomic mass | 58.693 u | 58.933 u |
| Density | 8.908 g/cm³ | 8.9 g/cm³ |
| Melting point | 1455 °C | 1495 °C |
| Boiling point | 2730 °C | 2927 °C |
| Electronegativity | 1.91 | 1.88 |
| First ionisation energy | 737.1 kJ/mol | 760.4 kJ/mol |
| Electron configuration | [Ar] 3d8 4s2 | [Ar] 3d7 4s2 |
| Discovered by | Axel Fredrik Cronstedt | Georg Brandt |
Nickel
Nickel takes its name from a German miners' curse. Ore that looked like copper but yielded none was called kupfernickel, roughly Old Nick's copper, after a mischievous spirit. The metal hiding inside it turned out to be one of the most useful of all. It resists corrosion, stays tough in the cold, takes a bright polish and, alloyed with chromium and iron, makes the stainless steel that is both rust-proof and easy to shape.
- The Sudbury nickel deposits in Canada formed when a huge meteorite struck around 1.85 billion years ago, melting the crust and letting metal-rich magma pool.
- The American nickel coin is 75 per cent copper and only 25 per cent nickel.
Cobalt
For most of history cobalt meant one thing: blue. Cobalt compounds gave Egyptian glass, Persian tiles, Chinese porcelain and Dutch Delftware their deep blue colours long before anyone knew the metal existed. Today cobalt has a very different reputation, as the critical metal in rechargeable batteries, jet engines and cancer treatment, and as a metal whose mining raises hard ethical questions.
- Cobalt, isolated in 1735, was the first metal to be discovered since ancient times.
- Vitamin B12 is the only vitamin that contains a metal atom, a single cobalt at its centre.
Colour the bubbles by density or melting point and the difference jumps out.
More comparisons
Data from Periodic-Table-JSON (CC BY-SA); temperatures rounded to the nearest degree. Written by Anthony.