93
Np
Neptunium
237
Neptunium
ACTINIDE
Bohr Model: Electrons arranged in energy shells around the nucleus.
Neptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus.
Quick Facts
Atomic Number 93
Period 7
Group 7
Phase Solid
Appearance silvery metallic
About Actinides
Actinides are the 15 metallic elements with atomic numbers 89–103. All actinides are radioactive.
History
Discovered By Edwin McMillan
Named By Unknown
Physical Properties
Atomic Mass 237
Density 20.45 g/L
Molar Heat 29.46 J/(mol·K)
Phase Transition (Melting & Boiling Points)
Neptunium melts at 912 K and boils at 4447 K.
Atomic Properties
Electron Config [Rn] 5f4 6d1 7s2
Electronegativity 1.36
Electron Affinity 45.85 kJ/mol
Ionization Energy 604.5 kJ/mol
Orbital Filling Diagram
This diagram visualizes electron configuration according to the Aufbau principle and Hund's rule.
Boxes represent orbitals (s, p, d, f), while arrows indicate electrons with spin up or down.
Electrons fill lower energy levels first and occupy orbitals singly before pairing.
Photograph
External Resources
Study Guide
Atomic Number
The number of protons in the nucleus, which defines the element.
Atomic Mass
The average mass of an atom, including protons and neutrons.
Electronegativity
A measure of how strongly an atom attracts electrons in a bond.
Ionization Energy
The energy required to remove an electron from an atom.
Electron Config
The arrangement of electrons in the atom's energy shells.