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Information valid for Np-237 unless otherwise noted

Basic Information

Symbol: Np
Atomic Number: 93
Mass: (237.0)
Melting Point: 640.0 C
Boiling Point: 3902.0 C
Number of Protons/Electrons: 93
Number of Neutrons: 144
Classification: Rare Earth
Crystal Structure: Orthorhombic
Density @ 293 K: 20.45 g/cm3
Color: Unknown

Atomic Structure

[Bohr Model of Neptunium]
Number of Energy Levels: 7

  1. First Energy Level: 2
    Second Energy Level: 8
    Third Energy Level: 18
    Fourth Energy Level: 32
    Fifth Energy Level: 23
    Sixth Energy Level: 8
    Seventh Energy Level: 2


Isotope Half Life
Np-235 1.08 years
Np-236 155000.0 years
Np-236m 22.5 hours
Np-237 2140000.0 years
Np-238 2.11 days
Np-239 2.35 days
Np-240 1.03 hours
Np-240m 7.22 minutes


Date of Discovery: 1940
Discoverer: E.M. McMillan
Name Origin: After the planet Neptune
Uses: No uses known
Obtained From: Man-made