Mendelevium (Md)
Mendelevium is element 101, an actinide in the actinide series (period 7). A neutral atom has 101 protons, 157 neutrons and 101 electrons, 2 of them valence electrons.
Actinide- Atomic number
- 101
- Atomic mass
- [258] u
- Valence electrons
- 2*
- Protons · neutrons
- 101 · 157
- Electrons per shell
- 2, 8, 18, 32, 31, 8, 2
- At room temperature
- solid
Bohr model of mendelevium
The Bohr model draws mendelevium as a nucleus of 101 protons and 157 neutrons, with its 101 electrons on 7 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 31 in shell 5, 8 in shell 6, 2 in shell 7. Press Build the atom to watch the shells fill from the inside out. The outer ring (the Q 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 mendelevium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹³
Short form (noble gas notation): [Rn] 7s² 5f¹³. The [Rn] stands for the electrons of radon, the noble gas before it.
How many valence electrons does mendelevium have?
Mendelevium has 2 valence electrons.
Mendelevium is a actinide, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 7), and electrons in its inner f and d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 101 | equal to the atomic number |
|---|---|---|
| Electrons | 101 | equal to the protons in a neutral atom |
| Neutrons | 157 | mass number 258 − 101 protons (for its longest-lived isotope, Md-258) |
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.
Mendelevium properties
| Symbol | Md |
|---|---|
| Category | Actinide |
| Group · period · block | — · 7 · f |
| Atomic mass | [258] u |
| State at 25 °C | solid |
| Melting point | 1,100 K (827 °C, 1,520 °F) |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius | — |
| First ionization energy | 6.58 eV |
| Electron affinity | — |
| Oxidation states | +3, +2 |
| Common ion charge | +3, +2 |
| Discovered | 1955 by Lawrence Berkeley National Laboratory |
Where mendelevium sits on the periodic table
Actinides: Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium.
Questions about mendelevium
How many valence electrons does mendelevium have?
Mendelevium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does mendelevium have?
A neutral mendelevium atom has 101 protons and 101 electrons. Its most common form has about 157 neutrons (mass number 258 − 101 protons).
What is the electron configuration of mendelevium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹³, written in short form as [Rn] 7s² 5f¹³.
What does the Bohr model of mendelevium look like?
A nucleus of 101 protons and 157 neutrons, circled by 7 electron shells holding 2, 8, 18, 32, 31, 8, 2 electrons.
What is the atomic number of mendelevium?
101. The atomic number is the number of protons in the nucleus, and it is what makes an atom mendelevium.