All practice pages/Interatomic theory/Elements
Element 93, an actinide
The first element heavier than uranium, named for the next planet out.
Period 7, in the actinide row set below the main table. The other actinides are tinted, and every cell opens its own article.
Neptunium has 93 electrons, one for every proton, so the atom carries no charge. Below are the same 93 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f⁴ 6s² 6p⁶ 6d¹ 7s²
Short form: [Rn] 5f⁴ 6d¹ 7s², where [Rn] stands for the 86 electrons radon already has.
That list runs by shell. In the order the subshells fill it reads [Rn] 7s² 5f⁴ 6d¹, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.
Neptunium sits in period 7 and has 7 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones neptunium can lose, gain or share, so they are the ones that decide what it bonds with.
Radioactive, like every actinide. It gives up electrons to form positive ions.
Tiny traces form in uranium ores. Nearly all of it comes from spent nuclear fuel.
Edwin McMillan and Philip Abelson made it in 1940 at Berkeley by bombarding uranium with neutrons, the first element beyond uranium. Uranium had been named for Uranus, so they named this one for Neptune.
Neptunium-237 is irradiated to make plutonium-238 for spacecraft power sources, and it goes into some neutron detectors.
Radioactive, and it builds up in bone and the liver.