Protons give the positive charge to the nucleus of an atom.
The atom is the smallest unit of matter that is composed of three sub-atomic particles: the proton, the neutron, and the electron. Protons and neutrons make up the nucleus of the atom, a dense and positively charged core, whereas the negatively charged electrons can be found around the nucleus in an electron cloud.
The Structure of Atoms
An atom consists of a positively charged nucleus surrounded by one or more negatively charged particles called electrons. The number of protons found in the nucleus equals the number of electrons that surround it, giving the atom a neutral charge (neutrons have zero charge). Most of an atom’s mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. Although the nucleus is heavy, it is small compared with the overall size of an atom.
The radius of a typical atom is around 1 to 2.5 angstroms (Å), whereas the radius of a nucleus is about 10-5 Å. If an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily fit inside a small football stadium.The nucleus of an atom contains protons and neutrons. Protons and neutrons have nearly equal masses, but they differ in charge. A neutron has no charge, whereas a proton has a positive charge that exactly balances the negative charge on an electron. Table 1 lists the charges of these three sub atomic particles, and gives their masses expressed in atomic mass units. The atomic mass unit (amu) is defined as exactly one-twelfth the mass of a carbon atom that has six protons and six neutrons in its nucleus. On this scale, protons and neutrons have masses that are close to, but not precisely, 1 u each. In fact, there are 6.022 x 1023 u in 1 gram. This number is known as Avogadro’s number, N. The number of protons in the nucleus of an atom is known as the atomic number, Z. It is the same as the number of electrons around the nucleus of the electrically-neutral atom. The mass number of an atom is equal to the total number of protons and neutrons.
When two atoms are close enough to combine chemically and form chemical bonds with one another, each atom “sees” the outermost electrons of the other atom. These outer electrons, called valence electrons, are the most important factors in the chemical behavior of atoms. Both the neutron and the proton have key roles in the characteristics of an atom. The number of neutrons determine the type of isotope the element could be and the proton determines the number of electrons that surround its nucleus.
All atoms with the same atomic number exhibit the same chemical behaviors and are classified as the same chemical element. Each element has its own name and a one- or two-letter symbol (usually derived from the element’s English or Latin name). For example, the symbol for carbon is C, and the symbol for calcium is Ca. It is important to note that for elements with two letters, the first letter is capital and the second letter is lowercase. The symbol for sodium is Na—the first two letters of its Latin (and German) name, natrium—to distinguish it from nitrogen, N, and sulfur, S.