Mendelevium (Md)

Mendelevium properties

Atomic number

101

Atomic mass

258 u

Category

Actinide

Group

—

Period

7

Block

f-block

State at room temp.

Solid

Electronegativity

1.3

Melting point

1,100 K (826.8 °C)

Boiling point

—

Density

—

Valence electrons

2

Common charges

+2, +3

Oxidation states

+3, +2

Atomic radius

—

Ionization energy

6.58 eV

Electron affinity

—

Radioactive

Yes, no stable isotopes

Discovered

1955

Mendelevium electron configuration

The electron configuration of Mendelevium (Md) is [Rn] 5f13 7s2. Its 101 electrons are arranged in shells as 2, 8, 18, 32, 31, 8, 2.

Protons, neutrons and electrons in Mendelevium

A neutral Mendelevium atom has 101 protons and 101 electrons. Most Mendelevium atoms have about 157 neutrons: the atomic mass rounded to 258, minus the atomic number 101.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Mendelevium have?

2

Mendelevium has 2 valence electrons in its outermost shell. As an f-block element, its 4f or 5f electrons can also take part in bonding.

See every element: Periodic table with valence electrons

Mendelevium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Mendelevium

258 g/mol

One mole of Mendelevium atoms (6.022 × 10²³ atoms) has a mass of 258 grams. Use this value to convert between grams and moles.

Mendelevium facts

• The first experiments in 1955 produced only 17 atoms of mendelevium in total.
• Its longest-lived known isotope, mendelevium-258, has a half-life of about 51 days.
• Mendelevium (Md) has atomic number 101 and is a solid at room temperature. It was discovered in 1955.

Position in the periodic table

Mendelevium is element 101, in period 7 of the periodic table. It is one of the Actinides in the f-block, shown in the rows below the main table.

All actinides

Uses of Mendelevium

Mendelevium has no uses outside scientific research. It is made a few atoms at a time by bombarding einsteinium or other heavy targets in particle accelerators. Chemists use these atoms to study how the heaviest actinides behave, such as mendelevium's ability to form +2 as well as +3 ions in solution.

Who discovered Mendelevium?

Albert Ghiorso, Bernard Harvey, Gregory Choppin, Stanley Thompson and Glenn Seaborg first made mendelevium in 1955 at Berkeley by bombarding einsteinium with alpha particles. It was named after Dmitri Mendeleev, creator of the periodic table.

Where does the name come from?

Mendelevium honors Dmitri Mendeleev, the Russian chemist who published the first widely recognized periodic table in 1869 and used it to predict elements that had not yet been discovered.

Discovery timeline