Sodium is element number 11, with the symbol Na. Table salt is sodium chloride, sodium joined with chlorine. In the body, sodium does important work in the fluid outside our cells.
Atomic number 1122.99
NaSodiumナトリウム (natoriumu)
Symbol
Na
Atomic weight
22.99
Place in the table
Period 3 · Group 1
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
English says sodium, the symbol says Na
The symbol is Na because it comes from the Latin name natrium, not from the English word.
Natrium comes from natron, a natural soda. The English word “sodium” comes from a Latin word for a headache remedy. The Japanese name, ナトリウム (natoriumu), follows the Latin side, the same as the symbol.
Table salt and the number 2.54
Sodium is the main positive ion in the fluid outside our cells, and it helps keep the amount of that fluid steady.
In Japan, the sodium in food is converted into an amount of salt. The Ministry of Health’s formula is sodium weight × 2.54 = salt weight. The 2.54 is 58.5 (the molar mass of salt, NaCl) divided by 23 (the molar mass of sodium).
In Japanese eighth-grade science, heating sodium hydrogen carbonate, a substance also used in daily life, is one of the example experiments.
Think about it
Q1If a food label says “sodium 400 mg,” about how many grams of salt is that?
Q2Find other elements whose names are different in different languages.
Q3If you let the water evaporate from salt water, what is left?
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Sodium and potassium (K) are in the same column of the periodic table, Group 1. In the body, sodium is the main positive ion outside the cells, and potassium is the main one inside.