It is known that hydrogen _____ (be) the lightest element.
举一反三
- Hydrogen is the most _____ element in the known Universe.
- _____ is the first element on the periodic table, making it the lightest element. Since it is so light, it rises in the atmosphere and is therefore rarely found in its pure form.
- 氢是已知的最轻的元素。Hydrogen is the lightest element________.?
- The element immediately following hydrogen is helium, the atom ____ which contains two electrons.
- （ ）is the most abundant chemical element in plants and animals. A: Oxygen B: Carbon C: Hydrogen D: Nitrogen