proton
Physics term for the positively charged subatomic particle in an atomic nucleus.
A proton is an elementary particle with a positive charge.
The nucleus of a hydrogen atom consists of a single proton.
陽子 is the positively charged particle in the nucleus, while 電子 is the negatively charged particle orbiting it.
陽子 carries a positive charge, whereas 中性子 has no charge, though both sit together in the atomic nucleus.
From 陽 (positive, yang) + 子 (small thing, particle), a calque of English 'proton' or German 'Proton'. The kanji 陽 reflects the positive charge.