Neptunium is element number 93, with the symbol Np. Its name comes from Neptune, the god of the sea in Roman myth, and the planet named after him.
Atomic number 93(237)
NpNeptuniumネプツニウム (neputsuniumu)
Symbol
Np
Atomic weight
(237)
Place in the table
Period 7 · Actinoids
The number in parentheses is not an atomic weight. It is the mass number of one radioactive isotope of the element.
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
The sea god and the planet Neptune
Neptunium was discovered in 1940. Following uranium (92, Uranus), it was named after Neptune. Plutonium (94) was also discovered in 1940.
Where it sits on the table
The fifteen elements from actinium to lawrencium are called the actinoids. On the Room of the Elements table they are in the lower of the two rows set apart at the bottom.
Think about it
Q1Do you think matching the order of the planets to the order of elements was a good idea?
Q2Where else is the sea god’s name used?
Q3Look up which elements were found in 1940.
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Neptunium, plutonium and astatine were all discovered in 1940.