It's called a pH indicator.
Answer: The answers are:
The number of protons in an atom of an element is unique to each element.
A proton in an atom of one element is identical to a proton in an atom of another element.
Explanation: The number of protons in an atom of an element is unique to each element. The number of protons in an atom of an element is the atomic number of that element. Atomic number determines the chemical properties and reactivity of the atom.
All atoms are made up of three particles: protons, electrons and neutrons. These particles are identical in all the elements, what distinguishes one element from another is the number of each of these particles it contains. Therefore, a proton in an atom of one element is identical to a proton in an atom of another element likewise the electrons and neutrons.
It's the law! Matter cannot be created or destroyed in chemical reactions. This is the law of conservation of mass. In every chemical reaction, the same mass of matter must end up in the products as started in the reactants.
