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GEN CHEM CHAPTER 1 NOTES
General Chemistry I (CHE 1103)
The University of Texas at San Antonio
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Gen Chem - Chapter 2
2 Elements, Compounds, and Mixtures: An Atomic Overview Definitions for Components of Matter - Element: the simplest type of substance with unique physical and chemical properties. Consists of only one type of atom. It can be broken down into any simpler substances by physical or chemical means
- Molecule: a structure that consists of t wo or more atoms that are chemically bound together and thus behaves as an independent unit
- Compound: a substance composed of t wo or more elements that are chemically combined
- Mixture: a group of t wo or more elements and/or compounds that are physically intermingled 2 The Observation That Led to an Atomic View of Matter Law of Mass Conservation
- total mass of substances present does not change during a chemical reaction — reactant 1 + reactant 2 —> Products Total mass Total mass Law of Definite (or Constant) Composition - Law of definite (or constant) composition: no matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass Law of Multiple Proportions
- If elements A and B react to form t wo compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers Example: Carbon Oxides I & II — Carbon Oxide I: 57% oxygen and 42% carbon — Carbon Oxide II: 72% oxygen and 27% carbon 2 Dalton’s Atomic Theory
- all matter consists of atoms; tiny invisible particles of an element that cannot be created or destroyed
- Atoms of one element cannot be converted into atoms of another element
- Atoms of an element are identical in mass and other properties and are different from the atoms of any other element
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- Compounds result from the chemical combination of a specific ratio of atoms of different elements Dalton’s Atomic Theory and Mass Conversion
- Mass conservation — postulate 1: Atoms cannot be created or destroyed — postulate 2: or converted into other types of atoms — postulate 3: since every atom has a fixed mass, during a chemical reaction the same atoms are present but in different combinations; therefor there is no mass change at all
Dalton’s Atomic Theory and Definite Composition - Definite composition: — postulate 4: atoms are combined in compounds in specific ratios — postulate 3: and each atom has a specific mass - each element constitutes a fixed fraction of the total mass in compound Dalton’s Atomic Theory and Multiple Proportions
- Multiple Proportions: — postulate 3: Atoms of an element have the same mass — postulate 1: and atoms are indivisible
- when different numbers of atoms of elements combine, they must do so in ratios of small, whole numbers
2 The Observation That Led to the Nuclear Atom Model
Observations that established the properties of cathode rays 1. Ray bends in magnetic field—> consists of charged particles 2. Ray bends towards (+) plate—> consists of negative particles 3.
- Millikan’s oil-drop experiment for measuring an electron’s charge
- Millikan’s findings were used to calculate the mass of an electron — mass of electron= mass ( as determined by J. Thompson) Charge
x Charge
- Rutherford’s a-scattering experiment and discover of the atomic nucleus Structure of the Atom
- the atom is an electrically neutral, spherical entity composed of a positively charged central nucleus surrounded by one ore more negatively charged elections
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Formation of a covalent bond bet ween t wo H atoms - Covalent Bonds form when elements share electrons, which usually occurs bet ween nonmetals
Molecules and Ions
- Molecule: the basic unit of a molecular element or covalent compound, consisting of t wo or more atoms bonded by the sharing of electrons. Most covalent substances consist of molecules
- Ion: a single atom or covalently bonded group of atoms that has an overall electrical charge. There are no molecules in an ionic compound
Elements that occur as molecules
- diatomic molecules: H2, N2, O2, F2, Cl2, Br2, I
- tetratomic molecules: P
- octatomic molecules: S8, Se The Carbonate ion in calcium carbonte
- a polyatomic ion consists of t wo or more atoms covalently bonded together and has an overall charge. In many reactions the polyatomic ion will remain together as a unit
Chemical Formulas - a chemical formula consists of element symbols with numerical subscripts - the chemical formula indicates the type and number of each atom present in the smallest unit of a substances
Naming Binary Ionic Compounds
- for all ionic compounds, the name and formula lists the cation first and the anion second
- in a binary ionic compound, both the cation and the anion are monatomic
- the name of the cation is the same as the name of the metal
- the anion is named by adding the suffix -ide to the root of the nonmetal name 2 Compounds of Metals That Form More Than One Ion
- many metals can form more than one ion
- ionic compounds of these elements that form only one monoatomic ion with the addition of a roman numeral within parentheses immediately following the metal ion’s name to indicate its charge
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2 Naming Compounds Containing Polyatomic Ions
- ionic compounds containing polyatomic ions are named like binary ions are named like binary ionic compounds except that the name of the polyatomic ion is used with the suffix -ide unless the name of the polyatomic ion already contains that suffix
- examples: KNO2: potassium nitrate — Cr2(CO3)3: Chromium(II) carbonate
Naming oxoanions
- If the number of oxygens is higher: — per; ate
- if the number of oxygens is lower: — hypo: ite
Numerical Prefixes for Hydrates and Binary Covalent Compounds 1. Mono- 2. Di- 3. Tri- 4. Tetra- 5. Penta-
- Hexa-
- Hepta-
- Octa-
- Nona-
- Deca-
2 Naming Binary Acids
- Binary Acid Solutions form when certain gaseous compounds dissolve in water
- example: gaseous hydrogen chloride, HCl, dissolves in water to form Hydrochloric acid
- hydrogen combines with an anion that has an -ide suffix
- Binary acids are named as follows: — prefix hydro- + anion nonmetal rot + suffix -ic + the word acid — hydro + chlor + ic + acid Naming Oxoacids Acids
- Oxoacids are compounds containing hydrogen and an oxoanion
- oxoacid names are similar to those of the oxoanions, except for t wo suffix changes: — -ate in the anion becomes -ic in the acid — -ite in the anion becomes -ous in the acid
- to name oxoacids: — oxyanion root + suffix -ic or -ous + the word acid
- the oxoanion prefixes hypo- and per- are retained — BrO4- is perbromate, and HBrO4 is perbromic acid — BrO2- is bromite, and HBrO2 is bromous acid Naming Binary Covalent Compounds
- binary covalent compound is typically formed by the combination of t wo nonmetals
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crystallization: separation is based upon differences in solubility of the components in a mixture
distillation: separation is based upon differences in volatility, the tendency of a substances to become a gas
chromatography: separation is based upon differences in solubility in a solvent versus a stationary phase
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GEN CHEM CHAPTER 1 NOTES
Course: General Chemistry I (CHE 1103)
University: The University of Texas at San Antonio
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