How Does Water Hold Itself Together?
The starring roles in water chemistry, apart from water molecules themselves, are played by the dissolved CO₂ from the atmosphere and the calcium and magnesium salts from the bedrock. To understand properly how these substances dissolve into your water — and how they sometimes undissolve — you need to understand how water molecules hold themselves together.
An atom consists of a positively charged nucleus surrounded by negatively charged electrons. A key to the way an atom behaves in a chemical reaction is the number of electrons it has. The electrons in an atom are arranged in a series of ‘shells’ — energy levels that can contain a fixed number of electrons.