What is the atomic number of Neptunium?

Neptunium has atomic number 93, which means a neutral atom has 93 protons and 93 electrons.

What is the chemical symbol for Neptunium?

The chemical symbol for Neptunium is Np.

What category is Neptunium in?

Neptunium is classified as a actinide and sits in period 7 of the periodic table.

Element 93

Neptunium (Np)

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.

Atomic Number

Atomic Mass

237 u

Period

Group

Actinide series

Phase

solid

Density

20.45 g/cm3

Electron Shells

2, 8, 18, 32, 22, 9, 2

Atomic Structure

Protons: 93. Electrons: 93. Neutrons: Varies by isotope.

Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁴ 6d¹

Why Neptunium Matters

Neptunium helps connect atomic number 93, actinide behavior, period 7 trends, and electron shell structure. Its solid phase, atomic mass of 237 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁴ 6d¹ make it useful for comparing bonding patterns across the periodic table.

Discovery and Occurrence

Neptunium was discovered 1940 by Edwin McMillan, Philip H. Abelson. 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.

Safety and Handling Context

Neptunium has radioactive isotopes or is commonly discussed with radioactive materials. Use this page as an educational reference; real samples require qualified supervision and controlled handling.

Related Elements

Frequently Asked Questions

What is the atomic number of Neptunium?: Neptunium has atomic number 93, which means a neutral atom has 93 protons and 93 electrons.
What is the chemical symbol for Neptunium?: The chemical symbol for Neptunium is Np.
What category is Neptunium in?: Neptunium is classified as a actinide and sits in period 7 of the periodic table.

Explore Neptunium in 3D

Use the interactive table above to rotate atomic models, compare periodic trends, and move from Neptunium to neighboring elements without losing your place.