Exam # 1 Study GuideChapter 2Atom - smallest chemical unit of matter; consists of 3 subatomic particles: protons, neutrons, and electronsProton - carries relative charge of +1Neutron - carries no electrical chargeElectron - carries relative charge of -1; account for most of the volume of anatomAtomic nucleus - very small region of high density at the center of the atom; neutrons and protons inside, electrons surrounding it*Mass of atom almost entirely accounted for by dense nucleus of protons and neu-trons Chem 111General Chemistry, First Edition by Vin-ing, Young, Day, andBotchAtomic mass unit (u) - 1/12 the mass of a carbon atom that contains six protons and six neutrons. Protons and neutrons have mass of 1 u and elec-trons have mass of 0 on atomic mass unit scale.*When an atom has more protons than electrons and has overall positive charge, it is called a cation.*When an atom has more electrons than protons and has an overall negativecharge, it is called an anion.Atomic number (Z) - the number of protons in the nucleusMass number (A) - number of protons and neutrons in the nucleusAtomic symbol (aka nuclear symbol) - one or two letter symbols that repre-sents the element along with the atomic number, written as a subscript, and the mass number, written as a superscript*All atoms of a given element have the same number of protons, but the number of neutrons can vary.Isotopes - atoms that have the same atomic number but different mass numbers; named using the element name and the mass numberAtomic weight (aka atomic mass) - average mass of all naturally occurring isotopes of that element; weighted average of the atomic masses of all iso-topes for a particular elementPercent abundance - percentage of atoms of a natural sample of the pure element represented by a particular isotope; used to describe isotope com-position for an elementEx: Chlorine has 2 naturally occurring isotopes, 35Cl and 37Cl. Percent abundance is 75.78% 35Cl and 24.22% 37Cl. So in any sample of chlo-rine, about 3/4 of the atoms are 35Cl and about 1/4 are 37Cl. Since there are more 35Cl atoms than 37Cl, the average mass of chlorine is closer to thatof 35Cl.Calculate the average atomic weight for chlorine:Chlorine-35 (34.96885 u, 75.78% abundant) and Chlorine-37 (36.96590 u. 24.22% abundant)Periodic Table:Groups - verti- cal columns; elements within each group have similar chemical and physical propertiesPeriods - horizontal rows; there are 7; portions of periods 6 and 7 are placedbelow the main body of the periodic table to make it fit on one pageLanthanides and Actinides - the portion of periods 6 and 7 that are placedbelow the main bodyAlkali metals - Group 1A elements; shiny solids that react with air, water, and halogensHalogens - Group 7A elementsAlkaline earth metals - Group 2A elements; most react with water to form alkaline solutionsNoble gases - Group 8A; least reactive elements in the periodic tableMain-group elements - elements in A groups, also called the representa-tive elementsTransition metals - elements in B groupsMetals - found on the left side of the periodic table; with the exception of mercury (Hg), they are shiny solids that are ductile and good conductors of electricityNonmetals - found on the right side of the periodic table; generally dull, brittle solids or gases that do not conduct electricityMetalloids or semimetals - found between metals and nonmetals; have properties of both metals and nonmetals*Most of the elements are solids. Only mercury and bromine are liquids at room temperature and 11 are gases at room temp. (hydrogen, nitrogen, oxy-gen, fluorine, chlorine, helium, neon, argon, krypton, xenon, and radon)*7 elements exist as diatomic molecules in their most stable form: H2, N2, O2, F2, Cl2, Br2, and I2. Allotropes - forms of the same element that differ in their physical and chemical properties; they are Carbon, Oxygen, Phosphorus, and SulfureEx: Red phosphorus - nontoxic, red color, burns in air at high tempsWhite phosphorus - white or yellow waxy solid that ignites in air above 50 degrees C, very poisonousWhich elements can exist as an extended, covalently bonded struc-ture?B, C, Si, Ge, P, As, Sb, Se, and TeThey are most of the metalloids and the nonmetals that border themCovalent compounds - consist of atoms of different elements held togetherby covalent bonds; characterized as either molecular covalent compounds ornetwork covalent compoundsEx: -Water is a molecular covalent compound because its made of individual H2O molecules, with the oxygen and hydrogen atoms in eachwater molecule held by covalent bonds -Silicon dioxide (SiO2) is a network covalent compound. Its made of a 3D network of silicon and oxygen atoms held together by covalent bondsMolecular for- mula - contains thesymbol for each element present and a subscript number to identify the number of atoms of each element in the moleculeEmpirical formula - represents the simplest whole-number ratio of ele-ments in a compoundEx: Hydrogen peroxide:Molecular formula - H2O2Empirical formula - HOWedge-and-dash model - 2D representation of a 3D structure that can easily be drawn on paper; bonds represented by lines (bonds that lie in planeof paper), wedges (bonds that lie in front of plane of paper), or dashes (bonds that lie behind plane of paper)Ball-and-stick model - shows atoms as colored spheres con- nected by sticks that repre-sent covalent bondsSpace-filling model - interpenetrating spheres rep-resent the relative amount of space occupied by each atom in the mole- cule*Covalent compounds can be categorized in many ways; two common classes are bi- nary nonmetals and inorganic acidsBinary nonmetals compounds - consist of only 2 elements, both non-metalsEx: H2O, CS2, and SiO2Rules for naming Binary Nonmetal Compounds:*Many binary nonmetal compounds have special names that have been used for many years.Hydrocarbons - binary nonmetal compounds containing only carbon and hydrogen; named according to the number of carbon and hydrogen atoms in the compound formulaInorganic acids - produce the hydro-gen ion (H+) when dissolved in wa-ter and are compounds that contain hy- drogen and one or more non- metals; can oftenbe identified by their chemical formulas because hydrogen is the first ele-ment in the compound formula; named as binary nonmetal compounds but without the use of prefixesOxoacids - groups of acids that differ only in the number of oxygen atoms; named according to the number of oxygen atoms in the