What Is Americium?
Americium is a chemical element with the symbol Am and atomic number 95, part of the radioactive actinide series.
A synthetic radioactive metal. Found in smoke detectors worldwide.
As a actinide in Period 7 and Group 3 (Transition Metals), americium's placement on the table reflects its electron configuration of [Rn] 5f⁷ 7s², which governs its bonding behavior and the type of compounds it typically forms.
Position on the Periodic Table
Americium is located in Period 7, the bottom row of the standard periodic table, consisting largely of radioactive and synthetic elements.
Within that row, americium sits in Group 3 (Transition Metals), alongside elements that share a similar number of valence electrons and, by extension, similar chemical behavior.
This position is not arbitrary — the periodic table was deliberately organized so that an element's row and column reveal its expected reactivity, bonding pattern, and physical state at a glance.
Physical & Chemical Properties
Americium has an atomic mass of (243) u and a density of 13.67 g/cm³. Its melting point is 1176°C and its boiling point is 2011°C.
Americium is radioactive, like every other member of the actinide series, with a nucleus prone to spontaneous decay.
Electron Configuration Explained
Americium's electron configuration is [Rn] 5f⁷ 7s², describing how its electrons are distributed across shells and subshells around the nucleus.
Reading the configuration in order shows electrons filling shells of increasing energy, following the standard Aufbau principle that explains how atomic structure builds up across the periodic table.
The outermost (valence) electrons shown in this configuration are what ultimately determine americium's chemical reactivity and the type of bonds it forms with other elements.
History & Discovery
Americium was formally discovered in 1944, G.T. Seaborg, identified through the careful isolation and analytical techniques typical of that era's chemical research.
Many elements from this period were anticipated by Dmitri Mendeleev's periodic table, which successfully predicted gaps corresponding to undiscovered elements well before laboratory instruments existed to confirm them directly.
What Is Americium Used For?
Americium's specific properties make it useful in several applications, including:
- Smoke detectors
- Medical imaging
- Neutron sources
- Nuclear medicine
- Research
These uses reflect americium's underlying classification as a actinide, since the same properties that define its category in chemistry also determine where it becomes practically useful.
Fun Facts About Americium
- Your smoke detector contains americium-241 — it ionizes air to detect smoke particles.
- Americium is element number 95 on the periodic table, in Period 7 and Group 3.
- Its standard atomic mass is (243) u, calculated from the natural abundance of its isotopes.
Frequently Asked Questions
What is Americium's atomic number?
Americium has atomic number 95.
What is Americium's chemical symbol?
Americium's symbol is Am.
What group and period is Americium in?
Americium is in Period 7, Group 3 (Transition Metals).
What is Americium's atomic mass?
Americium's standard atomic mass is (243) u.