Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Atomic Mass Review Sheet Atomic Number The atomic number is equal to the number of protons in an atom. Each element has a different atomic number. Do not get atomic number mixed up with atomic mass or atomic weight. Remember it this way, the atomic number is equal to the number of protons in an atom. The atomic number can be found on the periodic table: Symbol: Z Units: none Alternate names: proton number Mass Number The mass number is equal to the sum of the protons and neutrons in an atom. Remember it this way, the mass number is equal to the total number of protons plus neutrons. The mass number can be used to estimate atomic mass (see atomic mass below) The mass number is often indicated as a superscript in front of an atomic symbol. The atomic number is sometimes written as a subscript before the elemental symbol. Example: Mass number 12 6 C Atomic number Symbol: A Units: none Alternate names: atomic mass number www.ChemistryUnderstood.com Chemistry made simple. Oz Scott Halpern 2011 Isotope Isotopes are variations of elements that differ in the number of neutrons. Because they differ in number of neutrons, they also differ in mass number. Example: 12 13 12 6 C and 6 C are both isotopes of the element carbon. 6 C has 6 protons, 6 13 neutrons and a mass number of 12 (6+6 = 12). 6 C has 6 protons, 7 neutrons and a mass number of 13 (6+7=13). Atomic Mass The atomic mass is simply the mass of an atom. The atomic mass of an atom is about equal to the mass number of that atom expressed in amu. Example: 12 6 C has a mass number of 12. Its atomic mass is 12.00 amu. Units: atomic mass units (abbreviated u or amu) Atomic Weight The atomic weight is a weighted average of the isotopes of a particular element. Remember it this way, atomic weight is a weighted average. Units: none Molecular Mass The molecular mass is the mass of a molecule. It is calculated by adding together the atomic masses in the molecule. Units: amu Molar Mass The molar mass is the mass of an element or molecule present in 1 mole of the element or molecule. Remember it this way, the molar mass is a the mass of 1 mole of an element or molecule. The molar mass of an element is equal to the atomic weight expressed in g/mole. The molar mass of a molecule is calculated by adding together the atomic weights of the atoms in the molecule. Units: g/mole www.ChemistryUnderstood.com Chemistry made simple. Oz Scott Halpern 2011