Atomic Structure

• The proton number is sometimes called the atomic number, and has the symbol Z. No two elements have the same number of protons.
• The mass number is also called the nucleon number. It tells you how many protons and neutrons are in the nucleus.
• Changing the number of neutrons doesn't affect the atom's chemical properties, but it affects the stability of the nucleus. Unstable nuclei may be radioactive and decay over time into different nuclei that are more stable.
• Atoms with the same number of protons but different numbers of neutrons are called isotopes
• All living things contain the same percentage of radioactive carbon -14 taken in from the atmosphere. After they die, the amount of carbon -14 inside them decreases over time as it decays to stable elements. Scientists can calculate the approximate age of archaeological finds made from dead organic matter by using the isotopic data (amount of each isotope present) to find the percentage of radioactive carbon-14 that's left in the object.
• The specific charge of a particle is the ratio of its charge to its mass, given in coulombs per kilogram.

  Specific charge = charge/mass