Because in English, and most other western languages, we write from left to right. Using conventional numbering, you put the number before the object it relates to, so 2 He is two atoms of Helium. However, if you have a compound like Nitrogen, formed of two nitrogen atoms, writing 2 2N would be open to confusion. read more
The chemical order say O2H is never written over H2O since : - Water molecule is made up of 2 hydrogen atom and 1 oxygen atom. The chemical formula H2O strictly shows it that 2 hydrogen atoms are present to 1 oxygen atom. read more
Indeed PbCl2 is soluble in water but in a very small rate (9.9 g/L at 20 °C). In fact it is regarded as an water insoluble compound. One way to increase the solubility is as follows: Addition of chloride ions to a suspension of PbCl2 gives rise to soluble complex ions. read more
Without water, plants and many insects and arthropods could not survive, nor would humans have developed the foods and industries we have. Caring About Water To humans, as creators of our own lives, water is our servant. read more