Rhodium (Rh)
Rhodium is element 45, a transition metal in group 9, period 5. A neutral atom has 45 protons, 58 neutrons and 45 electrons, 1 of them valence electrons.
Transition metal- Atomic number
- 45
- Atomic mass
- 102.91 u
- Valence electrons
- 1*
- Protons · neutrons
- 45 · 58
- Electrons per shell
- 2, 8, 18, 16, 1
- At room temperature
- solid
Bohr model of rhodium
The Bohr model draws rhodium as a nucleus of 45 protons and 58 neutrons, with its 45 electrons on 5 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 16 in shell 4, 1 in shell 5. Press Build the atom to watch the shells fill from the inside out. The outer ring (the O shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of rhodium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁸
Short form (noble gas notation): [Kr] 5s¹ 4d⁸. The [Kr] stands for the electrons of krypton, the noble gas before it.
Rhodium breaks the usual filling order. The Aufbau rule predicts 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁷, but experiments show the configuration above. The energy levels of the subshells are so close here that a different arrangement wins.
How many valence electrons does rhodium have?
Rhodium has 1 valence electron.
Rhodium is a transition metal, so its valence electrons are less clear-cut than for main-group elements. It has 1 electron in its outermost shell (shell 5), and electrons in its inner d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 45 | equal to the atomic number |
|---|---|---|
| Electrons | 45 | equal to the protons in a neutral atom |
| Neutrons | 58 | mass number 103 − 45 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Rhodium properties
| Symbol | Rh |
|---|---|
| Category | Transition metal |
| Group · period · block | 9 · 5 · d |
| Atomic mass | 102.91 u |
| State at 25 °C | solid |
| Melting point | 2,237 K (1,960 °C, 3,570 °F) |
| Boiling point | 3,968 K (3,690 °C, 6,680 °F) |
| Density | 12.4 g/cm³ |
| Electronegativity (Pauling) | 2.28 |
| Atomic radius | 195 pm |
| First ionization energy | 7.459 eV |
| Electron affinity | 1.137 eV |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1803 by William Hyde Wollaston |
Where rhodium sits on the periodic table
Group 9: Cobalt, Iridium, Meitnerium.
Questions about rhodium
How many valence electrons does rhodium have?
Rhodium has 1 valence electron in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does rhodium have?
A neutral rhodium atom has 45 protons and 45 electrons. Its most common form has about 58 neutrons (mass number 103 − 45 protons).
What is the electron configuration of rhodium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹ 4d⁸, written in short form as [Kr] 5s¹ 4d⁸.
What does the Bohr model of rhodium look like?
A nucleus of 45 protons and 58 neutrons, circled by 5 electron shells holding 2, 8, 18, 16, 1 electrons.
What is the atomic number of rhodium?
45. The atomic number is the number of protons in the nucleus, and it is what makes an atom rhodium.