Chemistry 1201 Final Exam Study Guide Chapter 1 Intro Sig Figs another substance Physical properties can be observed without changing a substance into o Ex boiling point density mass volume etc Chemical properties can only be observed when a substance is changed into another substance o Ex flammability corrosiveness reactivity with acid etc Physical Changes Occurs when a substance changes shape size or color o Does not affect overall composition of the substance o Ex Changes of state grinding coffee liquid evaporating etc Chemical Changes result in new substances o Ex combustion oxidation decomposition etc salt dissolving in water Precision how closely the measurements agree with one another Accuracy how close the measurement is to the true value Significant figures all the digits of the measured quantity including the uncertain one last number o Ex 3 45 3 sig figs 4 3789999 8 sig figs o How to treat zeros Zeros between numbers are ALWAYS significant Ex 2 037 or 1023 4 sig figs Zeros at the beginning of the nonzero number are NEVER significant Ex 0 03 1 sig fig Dimensional analysis conversions of units require a conversion factor ratio o 1 kilo 1 x 103 o 1 milli 1 x 10 3 o 1 micro 1 x 10 6 o 1 nm 1 x 10 9m o 1 pm 1 x 10 12m o 1 fm 1 x 10 15m Chapter 2 Atoms Molecules and Ions Atomic Structure Atoms are composed of three fundamental subatomic particles protons neutrons and electrons o The nucleus of an atom which is very small contains all of the protons and neutrons It contains the majority of the mass of an atom Protons have a charge of 1 and neutrons have a zero charge Protons and neutrons are sometimes called nucleons o Electrons are negatively charged particles charge of 1 They exist outside of the nucleus of an atom Electrons occupy most of the volume of an atom They constantly move at very large velocities buzzing around the nucleus All atoms of the same element have the same number of protons the number of protons determines the element hence each element is designated an atomic number the number at the top of each element on the periodic table Isotopes atoms of the same element with the same number of protons but different numbers of neutrons Hence their mass numbers will be different o Naturally occurring substances are composed of a mixture of isotopes Mass number total number of nucleons i e Protons doesn t change and Neutrons does vary in the nucleus won t find this on periodic table Number of electrons equals number of protons ONLY FOR A NEUTRAL ELEMENT i e uncharged species Charge on an atom is determined by the balance between electrons 1 and protons 1 Charged atomic or molecular particles are called ions and result from the gain or loss of electrons only from the particle Neutral atoms or molecules are turned into positively charged ions called cations by removing one or more electrons Neutral atoms or molecules that gain extra electrons become negatively charged ions called anions o Ex 133 Cs Mass Number 133 Atomic Number 55 Number of Protons 55 atomic number Number of Neutrons 133 5 78 Number of Electrons atomic number charge the charge is 1 therefore 55 1 54 electrons Periodic Table used to organize the 112 elements in a meaningful way o Some groups in the periodic table are given special names 1A Alkali earth metals 1 2A Alkaline earth metals 2 6A Chalcogens 2 7A Halogens 1 8A Noble Gasses o Transition metals and post transition metals have variable o Metals are located on the left hand side of the periodic table Most of charges as cations the elements are metals Properties conduct heat electricity shiny high luster bendable malleable can be pounded into thin sheets likely to lose electrons when forming cations o Non Metals are located in the top right hand side of the periodic table Properties brittle many are gasses or powders do not conduct heat or electricity well likely to gain electrons forming anions o Elements with properties similar to both metals and non metals are called metalloids and are located at the interface between the metals and non metals Properties have physical properties between metals and non metals partially conduct electricity can be shiny but usually brittle semiconductor chips are based on these materials Molecular Formulas give the actual numbers and types of atoms in a molecule o Ex H2O Cl2 CH4 SO3 A molecule consists of two or more atoms bound together and each molecule has a chemical formula Molecular compounds consist of molecules o These molecules that make up molecular compounds are formed from non metals and include hydrogen Empirical formulas describe the simplest whole number ratio of atoms in a molecule which makes up the Molecular Compound o Ex H2O H2O H202 HO N2O4 NO2 Note The molecule H2O has the same empirical formula Ionic Compounds cation anion the majority of chemical reactions involve the transfer of electrons between species o Ex To form NaCl the neutral sodium atom Na must lose an electron o The electron cannot be lose entirely so it is transferred to a chlorine atom Cl which then becomes and anion Cl Cl e Cl o The Na and Cl ions are attracted to form an ionic NaCl lattice which to become a cation Na Na Na e crystallizes Na Cl NaCl For a neutral ionic compound the number of electrons lost and gained must balance so we must have the correct number subscripts of cations to balance with the anions Ex NaCl a 1 and a 1 neutral is a NaCl Names and Formulas for Cations o Know symbol name Cations formed from a metal have the same o If the metal can form more than one cation then the charge is name as the metal ion Ex K potassium ion indicated in parentheses in the name Ex Cu copper I ion Cu 2 copper II iom o Cations formed from non metals end in ium Ex NH4 ammonium ion Names and formulas for Anions o Monatomic anions with only one atoms are called name ending ide Ex Cl is chloride ion and S 2 is sulfide ion Exceptions hydroxide OH cyanide CN and peroxide ions O2 2 o Polyatomic anions with many atoms containing oxygen end in ate o Common Mono Bi atomic anion exceptions OH hydroxide ion CN cyanide ion 2 peroxide ion O2 O 2 oxide ion N 3 nitride ion or ite o Common Polyatomic anions chlorate ion nitrate ion 2 carbonate ion 2 chromate ion 2 dichromate ion 2 sulfate ion 3 phosphate ion 2 oxalate ion 3 borate ion ClO3 NO3 CO3 CrO4 Cr2O7 SO4 PO4 C2O4 BO3 MnO4 C2H3O2 permanganate ion acetate ion o The common polyatomic with oxygen is called name 1st element ending ate Ex NO3 is nitrate o Polyatomic anions containing oxygen