Indium is element number 49, a metal with the symbol In. Its name comes from indigo, a blue dye.
Atomic number 49114.8
InIndiumインジウム (injiumu)
Symbol
In
Atomic weight
114.8
Place in the table
Period 5 · Group 13
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
An indigo line of light
Indium was discovered in 1863 from an indigo line seen when light is split finely, and it was named for that color.
The word indigo is linked to a Greek word meaning “from India.”
Where it sits on the table
Indium is in the fifth row of Group 13, with gallium above and thallium below. Thallium is also named for the color of its light (green).
Think about it
Q1Look for things dyed with indigo around you.
Q2What else could identifying elements by the color of light be used for?
Q3Indium and thallium, both named for colors, share a column. Is that a coincidence?
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Elements named for their line colors were found one after another within a few years: caesium (1860), rubidium (1861), thallium (1861) and indium (1863).