1.原子核都是由质子和中子组成的.(H的原子核只有质子而无中子.)2.离子化合物中一定含有金属元素.(NH_4Cl是离子化合物,却不含金属元素.)3.非极性键都是存在于单质分子中.(化合物中也有非极性键,如H_2O_2、Na_2O_2)4.含有极性键的化合物一定是极性分子.(CO_2、CH_4等含有极性键,但它们却是非极性分子.)5.所有共价键部具有方向性.(H—H键没有方向性.) 1. The nucleus consists of protons and neutrons. (The nucleus of H has only protons but no neutrons.) 2. Ionic compounds must contain metal elements. (NH 4 Cl is an ionic compound, but it does not contain metal elements.) 3. Non-polar bonds are present in the elemental molecules. (The compounds also have non-polar bonds, such as H2O2, Na2O2) 4. Compounds containing polar bonds must be polar molecules. (CO_2, CH_4, etc. contain polar bonds, But they are non-polar molecules.) 5. All covalent bonds have directionality. (The H-H bond has no directionality.)