33
Room of the Elements · No. 33
Arsenic (As): what kind of element is it?
日本語
In short
Arsenic is element number 33, with the symbol As. Its name comes from orpiment, a yellow mineral that contains arsenic.
Atomic number 3374.92
AsArsenicヒ素 (hiso)- Symbol
- As
- Atomic weight
- 74.92
- Place in the table
- Period 4 · Group 15
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
Named for orpiment
The symbol As comes from the Latin arsenicum, from arsenikon, the Greek word for orpiment. Orpiment is a mineral of arsenic combined with sulfur.
The name is also said to be linked to a Greek word meaning “fierce.” Arsenic has been known since the Middle Ages.
Where it sits on the table
Arsenic is in the fourth row of Group 15. Directly above it is phosphorus, and above that, nitrogen.
Next door, in Group 16, is selenium, named after the Greek word for the Moon.
Think about it
- Q1Why do you think element names so often come from the color or shape of minerals?
- Q2How long ago were “the Middle Ages”?
- Q3Nitrogen, phosphorus and arsenic share a column. Look into how they are alike.
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Elements whose discovery is dated to the Middle Ages include arsenic, zinc, antimony and bismuth.