How to Write 砹 (ài) — Meaning “astatine”

Imagine a stone (石) with a mugwort plant (艾) growing out of it, and this unusual combination represents the rare element astatine. You can also think of the pronunciation ài as 'eye' and picture an 'astatine atom' that looks like a stone eye. This links the visual parts to the scientific meaning.

Start with the left part 石: write the horizontal stroke, then left-falling, vertical, horizontal fold, and finally the bottom horizontal (5 strokes). Then write the right part 艾: a horizontal stroke across the top, then the two vertical strokes downward, followed by a left-falling and a right-falling stroke (5 strokes total). A common mistake is making the top of 艾 too wide or confusing its grass radical with other shapes—keep the two vertical strokes parallel and the bottom strokes balanced.

砹 (ài) has the right side 艾 (mugwort), while 矸 (gān) has 干 (dry, or a work pole) and 矻 (kū) has 乞 (to beg). Visually, 艾's top is a grass radical (艹) with two vertical strokes and a cross below, where 干 is simply two horizontal lines and a vertical, and 乞 looks like a person bending. In meaning, 矸 refers to waste rock or gangue, 矻 means hard work or to exert, and 砹 is the element astatine—so they are completely different words despite sharing the 石 radical.

砹 is used almost exclusively in scientific or chemical contexts, such as in the words 砹原子 (astatine atom) or 元素砹 (the element astatine). It is not part of everyday vocabulary and does not appear in HSK lists. Culturally, astatine is the heaviest halogen and its name comes from Greek 'astatos' meaning unstable, matching its radioactive nature; the Chinese character follows the pattern of using 石 for solid elements, even though astatine is a halogen.

Common words containing 砹 include: 砹原子 (ài yuán zi) — astatine atom; 元素砹 (yuán sù ài) — the element astatine; 砹同位素 (ài tóng wèi sù) — astatine isotope.