How do protons determine the properties of an atom?
The number of protons determines the number of electrons.
The number of electrons, in turn, determines the chemical properties of the atom.
Protons contribute to the mass of an atom and provide the positive charge to the nucleus. The number of protons also determines the identity of the element.
Electrons have a negative charge. Since the atom is electrically neutral, the number of electrons must equal the number of protons.
The electrons arrange themselves in energy levels around the nucleus. The outermost or valence electrons of an atom are the ones that take part in chemical reactions. An element’s chemical properties depend on its valence electrons.
One to three valence electrons — tend to form positive ions.
Five to seven valence electrons — tend to form negative ions.
Four valence electrons — tend to form covalent bonds.