Atoms are made of smaller particles. An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. Electrons and protons have a property called electric charge, which affects the way they interact with each other and with other electrically charged particles. Electrons carry a negative electric charge, while protons have a positive electric charge. The negative charge is the opposite of the positive charge, and, like the opposite poles of a magnet, these opposite electric charges attract one another. Conversely, like charges (negative and negative, or positive and positive) repel one another. The attraction between an atom’s electrons and its protons holds the atom together. The nucleus contains nearly all of the mass of the atom, but it occupies only a tiny fraction of the space inside the atom. If an atom were magnified until it was as large as a football stadium, the nucleus would be about the size of a grape. Atoms of the same element that differ in mass number are called isotopes.
- particle [ˈpɑ:tikl] n.微粒
- electron [iˈlektrɔn] n.电子
- dense [dens] adj.密集的
- nucleus [ˈnju:kliəs] n. 原子核
- proton [ˈprəutɔn] n.质子
- neutron [ˈnju:trɔn] n.中子
- electric charge [iˈlektrik - tʃa:dʒ] n.电荷
- interact [ˌɪntərˈækt] v.相互作用
- negative [ˈneɡətiv] adj. 负的
- positive [ˈpɔzitiv] adj. 正的
- opposite [ˈɔpəzit] n. 对立物
- pole [pəul] n. 磁极，电极
- magnet [ˈmæɡnit] n.磁铁
- conversely [ˈkɔnvə:sli] adv.相反地
- like charges [laik - tʃɑ:dʒiz] n. 同性电荷
- attract [əˈtrækt] v. 吸引
- repel [riˈpel] v. 排斥
- attraction [əˈtrækʃən] n. 引力
- mass [mæs] n. 质量
- occupy [ˈɔkjupai] v. 占用
- fraction [ˈfrækʃən] n.小部分
- magnify [ˈmæɡnifai] v.放大
- stadium [ˈsteidjəm] n.体育场
- property [ˈprɔpəti] n. 性质
- grape [ɡreip] n.葡萄
- mass number [mæs - ˈnʌmbə] n.(原子)质量数
- isotope [ˈaisəutəup] n.同位素
