CHEM 1211K 1st Edition Lecture 5 Outline of Last Lecture I Chapter 2 Atoms and Elements Chapter 2 Atoms and Elements continued II Subatomic Particles Protons Neutrons and Electrons in Atoms A Each element has a unique number of protons in its nucleus B The number of protons in the nucleus of an atom is called the atomic number C the elements are arranged on the Periodic Table in order of their atomic numbers D Each element has a unique name and symbol E symbol either one or two letters F one capital letter or one capital letter and one lowercase letter 2 6 4 IONS When atoms gain or lose electrons they acquire a charge Charged atoms or groups of atoms are called ions When atoms gain electrons they become negatively charged ions called anions When atoms lose electrons they become positively charged ions called cations Ions behave much differently than the neutral atoms e g the metal sodium made of neutral Na atoms is highly reactive and quite unstable however the sodium cations Na found in table salt are very nonreactive and stable Because materials such as table salt are neutral there must be equal amounts of charge from cations and anions in them III Structure of Atom Anions Cations Nonmetals form anions For each negative charge the ion has one more electron than the neutral atom F 9 p and 9 e F 9 p and 10 e P 15 p and 15 e P3 15 p and 18 e Anions are named by changing the ending of the name to ide fluorine F 1e F fluoride ion oxygen O 2e O2 oxide ion Metals form cations For each positive charge the ion has one less electron than the neutral atom Na atom 11 p and 11 e Na ion 11 p and 10 e Ca atom 20 p and 20 e Ca2 ion 20 p and 18 e These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Cations are named the same as the metal sodium Na Na 1e calcium Ca Ca2 2e sodium ion calcium ion IV Divisions Groups of the Periodic Table Metals a Good conductors of heat and electricity b Malleable can be pounded into flat sheets c Ductile can be drawn into wires d Often shiny e Tend to lose electrons f Examples Chromium and Copper Nonmetals g Poor conductors of heat and electricity h Tend to gain electrons i Examples Oxygen and Carbon Metalloids j Mixed properties k Some are semiconductors intermediate and temperature dependent electrical conductivity l Examples Silicon and Germanium 1 Group 8A elements noble gases Mostly unreactive Examples Helium and Neon 2 Group 1A elements alkali metals Reactive metals Examples Sodium and Potassium 3 Group 2A elements alkaline earth metals Reactive but not as reactive as Group 1A Examples Magnesium and Barium 4 Group 7A elements halogens Very reactive nonmetals Example Chlorine and Bromine V Isotopes When Number of Neutrons Varies All isotopes of an element are chemically identical undergo the exact same chemical reactions All isotopes of an element have the same number of protons Isotopes of an element have different masses Isotopes of an element have different numbers of neutrons Isotopes are identified by their mass numbers which is the sum of all the protons and neutrons in the nucleus Current Lecture