The chemical formular for water is H2O.
The H aspect of the formula stands for hydrogen gas and the subscript 2 which is attached to the H symbol signifies that two atoms of hydrogen are joined together, that is two atom of hydrogen are present.
The chemical formula of water indicates that, two atom of hydrogen react with one atom of oxygen to form one molecule of water.
In chemical formulae, subscripts are normally used to indicate the number of atoms that are present in a molecule.
A fuse is an electrical safety device which should not blow, which should overheat and melts if current is too high. Its placed in the live wire before the switch. This prevents overheating and catching fire. A fuse have a specific current value for example - 3000 amps. So when choosing a suitable fuse you must use the above minimum value but less than maximum value. For example in a circuit there is 1000W flowing, you should choose more than 1000 amps fuse not less or else, it will melt.
An element refers to a collection of atoms having the same number of protons and electrons (an atomic number). In each element there is a different atomic number due to a different amount of protons in the nucleus.
An isotope is a variation of an element that contains a different number of neutrons, therefore adding weight to the atom.
An ion is a charged atom, and its charge shows how many electrons it needs to gain or lose in order to become stable.
Check-call-Care if you are training to be a life guard.
