Chemistry 1301A/B Study Guide - Final Guide: Mole Fraction, Unified Atomic Mass Unit, Sodium Chloride

• School: Western University
• Department: Chemistry
• Course: Chemistry 1301A/B
• Professor: Christina Booker

Document Summary

Isotopes are atoms with the same number of protons (so they are the same element) but with different numbers of neutrons. This different number of neutrons results in identical elements having different mass numbers: barium is element number 56. In a neutral atom, the number of electrons is equal to the number of protons, so this species has 56 electrons. The mass number of any element is the sum of the number of protons and the number of neutrons. Therefore, the number of neutrons in this isotope is 135 56 = 79: a charge of +1 means that the species has lost one electron. When this species is neutral it would have 11 electrons. If 69ga is 60. 4%, then the isotope xga is 39. 6%. Use the average atomic mass (from the periodic. Table) to determine the atomic mass of xga. Average atomic mass = [atomic mass 69ga x fraction 69ga] + [atomic mass xga x fraction xga]