Oxygen is element number 8, with the symbol O. About 20% of the air at ground level is oxygen. Water, too, is made of hydrogen and oxygen.
Atomic number 816.00
OOxygen酸素 (sanso)
Symbol
O
Atomic weight
16.00
Place in the table
Period 2 · Group 16
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
“Sour-source”
In Dutch, oxygen is zuurstof, meaning “sour-source.” Udagawa Yōan translated it into Japanese as 酸素 (sanso).
The idea goes back to the French chemist Lavoisier, who believed that every acid contains oxygen. The Latin oxygenium, the source of the symbol O, also combines the Greek for “acid” and “producing.”
But this turned out to be Lavoisier’s mistake. Even so, the name is still used today.
Oxidation and reduction
When a substance joins with oxygen, we call it oxidation. When oxygen is taken away, we call it reduction. In Japanese junior high school science, students confirm by experiment that both are reactions involving oxygen.
A set weight of copper or magnesium can only combine with a limited amount of oxygen. From this, students learn that substances combine in fixed ratios by weight.
Think about it
Q1A name born from a mistake is still used today. Why do you think it was never changed?
Q2Does a ten-yen coin turning dark have anything to do with oxidation?
Q3If the air were 40% oxygen instead of 20%, what might change?
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — The rocks and sand under our feet contain lots of oxygen. Silica (silicon dioxide) and other compounds of silicon and oxygen are the main materials of the Earth’s crust.