An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100pm (a ten-billionth of a meter, in the short scale). However, atoms do not have well-defined boundaries, and there are different ways to define their size that give different but close values.
近义、反义、联想词
近义词
n.
substance, matter, material, stuff
解析
molecule 指物质中保持原物质的一切化学性质,能独立存在的最小微粒,即分子。 atom 指元素的最小粒子,其体积比molecule小。 particle 指任何物质的微粒,引申指任何小的部分。 speck 一般指“微点”或“微粒”,可引申指“斑点、污点”。 grain 通常指能为肉眼清楚看到的颗粒,比上述几个词所表“粒”的体积大。