An electron cloud is a probabilistic picture of where an electron is likely to be found around the nucleus, with the density of the cloud at any point representing the probability of finding the electron there. It replaces the older idea of a fixed orbit with a smeared-out region of probability. Denser parts of the cloud correspond to higher electron probability density (ψ²).

电子云是电子在原子核周围可能出现位置的概率化图示,云在任一点的浓密程度代表在该处找到电子的概率。它用一团弥散的概率区域取代了固定轨道的旧观念。云中较浓密的部分对应较高的电子概率密度(ψ²)。