Americium (Am)
Americium is element 95, an actinide in the actinide series (period 7). A neutral atom has 95 protons, 148 neutrons and 95 electrons, 2 of them valence electrons.
Actinide- Atomic number
- 95
- Atomic mass
- [243] u
- Valence electrons
- 2*
- Protons · neutrons
- 95 · 148
- Electrons per shell
- 2, 8, 18, 32, 25, 8, 2
- At room temperature
- solid
Bohr model of americium
The Bohr model draws americium as a nucleus of 95 protons and 148 neutrons, with its 95 electrons on 7 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 25 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 americium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁷
Short form (noble gas notation): [Rn] 7s² 5f⁷. The [Rn] stands for the electrons of radon, the noble gas before it.
How many valence electrons does americium have?
Americium has 2 valence electrons.
Americium 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 | 95 | equal to the atomic number |
|---|---|---|
| Electrons | 95 | equal to the protons in a neutral atom |
| Neutrons | 148 | mass number 243 − 95 protons (for its longest-lived isotope, Am-243) |
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.
Americium properties
| Symbol | Am |
|---|---|
| Category | Actinide |
| Group · period · block | — · 7 · f |
| Atomic mass | [243] u |
| State at 25 °C | solid |
| Melting point | 1,449 K (1,180 °C, 2,150 °F) |
| Boiling point | 2,284 K (2,010 °C, 3,650 °F) |
| Density | 13.69 g/cm³ |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius | 244 pm |
| First ionization energy | 5.993 eV |
| Electron affinity | — |
| Oxidation states | +6, +5, +4, +3 |
| Common ion charge | +6, +5 |
| Discovered | 1944 by Glenn T. Seaborg |
Where americium sits on the periodic table
Actinides: Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Curium, Berkelium.
Questions about americium
How many valence electrons does americium have?
Americium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does americium have?
A neutral americium atom has 95 protons and 95 electrons. Its most common form has about 148 neutrons (mass number 243 − 95 protons).
What is the electron configuration of americium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁷, written in short form as [Rn] 7s² 5f⁷.
What does the Bohr model of americium look like?
A nucleus of 95 protons and 148 neutrons, circled by 7 electron shells holding 2, 8, 18, 32, 25, 8, 2 electrons.
What is the atomic number of americium?
95. The atomic number is the number of protons in the nucleus, and it is what makes an atom americium.