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Goal 5.02 Atomic Structure Protons, Neutrons, Electrons Name Symbol Location Charge Mass Proton p+ Nucleus +1 1amu Neutron n Nucleus 0 1amu Electron e- Cloud -1 1/2000amu Atomic Number Atomic number is the number of protons in an element. Atoms of the same element always have the same number of protons. Atomic numbers are found on periodic table beside element’s symbol. Mass Number Mass number is the number of protons plus the number of neutrons in an element. Unless specified, the number of p’s and n’s are equal and the mass number is twice that of the atomic number. Atom Notation A symbol is the abbreviation for an element’s name. They can be found on the periodic table. The typical notation for an atom includes the element’s symbol with atomic number in subscript to the left and mass number in superscript to the left. Isotope An isotope is an atom with a differing number of neutrons and therefore a different mass number. It can be written in normal notation or isotope notation. Isotope notation is the element’s symbol followed by a dash and the atomic mass. Atomic Mass The atomic mass of an element is the average of all the naturally existing isotopes of an element. It can be found on the periodic table under the element’s symbol. Ion An ion is an atom with a differing number of electrons and therefore an overall charge. The notation includes the charge written in superscript to the right of the element’s symbol. The charge can be determined by canceling protons and electrons to see what remains. Determining p,n,e Given the notation of an element you should be able to determine the number of p, n, and e. The first step is to find the element on the periodic table and determine its atomic number which gives you the number of p. The number of p’s will never change. From there you must determine the number of n and e. These may be different from the number of p and can be found by looking at notation of the element. Orbits Electrons orbit the nucleus in distinct levels called orbits. At ground state an orbits can hold…. The 1st orbit can hold 2 electrons. The 2nd can hold 8 electrons. The 3rd can hold 18 electrons. The 4th can hold 32 electrons. Drawing Atomic Structure The arrangement of electrons within their orbits can be shown using electron dot diagrams. Start by drawing a nucleus containing the correct number of protons and neutrons. Then determine the number of electrons within the atom. Draw the 1st orbit and fill that orbit with electrons. Electrons are drawn on the orbit line as a solid circle. Continuing drawing and filling orbits until the correct number of electrons is reached. Valence Electrons The electrons in the very outer orbit are called valence electrons. Valence electron diagrams are drawn by using dots that represent the valence electrons around the element’s symbol. Each side of the symbol can contain two dots.