Atomic Structure

Atoms are composed of three types of particules protons , neutrons, and electrons. Protons and Neutrons are responsible for atomic mass. 15oz are prottons and neutrons while only 1oz is only electrons. Always remember the mass of an electron is very small ( 9.108 X 10-28 grams). Protrons have a positive (+) charge while neutrons have no charges. They are  neutral. Electrons reside in orbitals around the nucleus. They have a negative charge (-). Remember this the number of protons determines the atomic number.The same element may contain varying numbers of neutrons; these forms of an element are called isotopes. The chemical properties of isotopes are the same, although the physical properties of some isotopes may be different. Some isotopes are radioactive-meaning they "radiate" energy as they decay to a more stable form, perhaps another element half-life: time required for half of the atoms of an element to decay into stable form. Another example is oxygen, with atomic number of 8 can have 8, 9, or 10 neutrons.