What Are the Positive Particles Found in the Nucleus of an Atom?
- The model of the atom has changed as new information about the atom was uncovered through experiments. Currently, the model of an atom is a densely packed nucleus of protons and neutrons held together by the strong nuclear force. Surrounding this nucleus is a cloud of electrons held to the atom by a Coulombic attraction between the negatively charged electrons and the positively charged protons in the nucleus.
- Each element has a specific number of protons given as the atomic number. While the number of neutrons varies between isotopes of an element and electrons may be gained or lost by the atom, the number of protons is constant for a given element. For example, the element hydrogen has three isotopes: hydronium with zero neutrons, deuterium with one neutron, and tritium with two neutrons. Each of these isotopes has only one proton, the defining characteristic of hydrogen.
- Physical and chemical reactions do not alter the number of protons in the nucleus. Nuclear reactions can change the number of protons in a nucleus producing a different element that corresponds to the new number of protons. In the sun, through a process called nuclear fusion, atoms of hydrogen each with one proton are fused together to form a nucleus containing two protons, the element helium. The reverse process can also occur with a nucleus fragmenting to produce two or more nuclei, each with a portion of the protons from the previous atom.
- Subatomic particles, such as protons, have an extremely small mass (1.6727 x 10 -24th g) yet are far more massive than electrons. Chemists often describe the mass of a proton or neutron as one atomic mass unit (amu). The mass of an atom is then considered as the sum of the protons and neutrons in the nucleus. For instance, carbon-12 is an isotope of carbon with six neutrons and six protons. The mass of one carbon-12 atoms is then 12 atomic mass units.
- Although the proton is a fundamental particle of atoms, the proton is itself a combination of three smaller elementary particles called quarks. A combination of three quarks is called a baryon. Protons specifically consist of two up quarks and one down quark. Neutrons are another type of baryon but differ in consisting of two down quarks and one up quark.