chemistry finisher

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  • 1. By: Johanna Louise B. Neri

2. Chapter 1. The Nature of ChemistryKey Concepts Chemistry - is the study of matter andthe changes it undergoes. It issometimes called the central sciencebecause it overlaps with many othersciences. Technology - is the application ofscience. It has improved the quality ofhuman life. SI units - are used to express physicalquantities in all sciences. Metric prefixesare used to make units smaller or larger. 3. Precision - is how close severalmeasurements are to the same value. Accuracy - tells how close ameasurement is to the true oraccepted digit. Significant - figures include both thecertain digits and the estimated digit. Scientific notation - is used to writevery small or very large numbers. 4. Dimensional analysis - is thetechnique that uses conversionfactors. The guide to ensure thatconversion factor are properlyformulated is the cancellation ofunits. 5. Chapter 2. Matter: Its Compositionand Organization. Key Concepts Matter - is anything that has massand volume. Properties of matterdiffer for solids, liquids, and gases. A pure substance is either an elementor a compound. An element is asubstance that cannot be broken downto simpler substances. A compound isformed when two or more elementscombine in a chemical change. 6. A change in the properties of substance without achange in composition is a physical change. Ifthere is a change in the composition of asubstance, a chemical change has occurred.Chemical changes produce matter with newproperties. The physical combination of two or moresubstances is a mixture. A mixture has a variablecomposition. It may be heterogeneous orhomogeneous. Heterogeneous mixtures (coarsemixtures, suspensions, and colloids) do not haveuniform properties throughout, whilehomogeneous mixtures (solutions) have uniformproperties. 7. Solutions may be gases, liquids, or solids. The components of a mixture can beseparate by physical methods. Colloids - are mixtures of two or moresolids, liquids, or gases whose particlesare bigger than the particles of asolution but smaller than those of asuspension. Tyndall effect, Brownianmovement, adsorption, and electricalcharge are the properties of colloids. 8. Colloids are prepared and purified bycondensation and dispersion methods. Condensation - is the process ofcombining molecules to form colloidalparticles. Dispersion - is the process of breakingdown large particles to colloidal size. Energy - is the capacity to do work or totransfer heat. It is involved whenevermatter undergoes a change. 9. Chapter 3. Atomic Theory.Key Concepts Over 2400 years ago, the concept of theatom was proposed by Greekphilosophers. In the early 19th century, Daltonsproposed the atomic theory. This theoryis related to the three fundamental lawsof matter. (1) The total mass of the reactants andproducts are constant during a chemicalreaction (law of conservation of mass). 10. (2) Any sample of compound, haselements in the same proportion (lawof definite composition). (3) In different compounds ofthe same elements, the mass of oneelement that combines with a fixedmass of the other can be expressedas a ratio of small whole numbers (lawof multiple proportions). 11. Thomsons experiment on the behavior ofcathode rays in magnetic and electricfield led to the discovery of the electronand the measurement of its charge tomass ratio. Millikans oil drop experiment measuredthe charge of the electron. Becquerel and the Curies discoveredradioactivity. Rutherfords studies on alpha rays led tothe discovery of nucleus. 12. Atoms have a nucleus that contains protonsand neutrons. Electrons move in the spacearound the nucleus. Elements can be classified by atomicnumber or the number of protons in thenucleus of an atom. All atoms of a given element have the sameatomic number. The mass number of anatom is the number of protons and neutrons. All atoms of the same element that differin mass number are known as isotopes. 13. Chapter 4. Electronic Configuration.Key Concepts The properties of visible light and otherforms of electromagnetic radiation led tothe electronic structure of atoms. Max Planck proposed that energy isabsorbed and emitted in discrete amountsor individual packets called quanta (pluralfor quantum). Albert Einstein used Plancks theory toexplain the photoelectric effect. Heproposed that light consists of quanta ofenergy which behave like tiny particles oflight. He called these energy quantaphotons. 14. The concept of quantized electrons grewfrom the study of line spectra of atoms. Aline spectrum consists of quanta of energywhich can be used like fingerprints toidentify the element. Niels Bohr used the line spectra to explainspecific energy levels within the atom. Heproposed the planetary model of the atom. Louis de Broglie discovered the wave natureof matter which initiated the developmentof a new mathematical description ofelectron configuration. 15. Heisenbergs uncertainty principle explained theimpossibility of simultaneously measuring themomentum and location of an electron. Erwin Schrodinger devised the quantummechanical model of the atom which describedelectrons as waves that exist in quantized energylevels. The regions in space around the nucleus whereelectrons are most likely to be found are calledorbitals. These orbitals have various shapes andare labeled s, p, d, and f. Each principal energylevel or shell consists of these orbitals. 16. The manner in which electrons are arrangedaround the nucleus of an atom is called electronconfiguration. The Aufbau principle, the Puali exclusionprinciple, and the Hunds rule are applied inwriting electron configurations. The Aufbau principle tells the sequence in whichorbitals are filled. The Pauli exclusion principle states that amaximum if only two electrons can occupy anorbital. Hunds rule explains that electrons pair up onlyafter each orbital on a sublevel is occupied by asingle electron. 17. Chapter 5. The Periodic Table.Key Concepts Different periodic table were developedbyDobereiner, Newlands, Mendeleev, andMeyer. The periodic table was based onsimilarities in properties and reactivitiesof elements in the increasing order oftheir atomic mass. Discrepancies in these periodic tableswere resolved when Moseley establishedthat each element has a unique atomicnumber and showed that elements shouldbe arranged according to theirincreasing atomic number. 18. The periodic table is organized into 18groups or families and 7 periods or rows.The groups are organized further intos, p, d, and f blocks based on how valenceelectrons fill each sublevel. Elements in agroup have similar properties becausethey have the same valence electrons. Atomic radius decreases from left toright across a period because thepositive charge of the atomsincreases, which attracts electrons morestrongly. 19. Atomic radius increases down a groupbecause the electrons of the atoms fillmore energy levels. Ionization energy - is the energyabsorbed to remove an electron to forma positive ion. Electron affinity - is the energy whenan atom gains an electron forming anegative ion. Electronegativity is the attraction of anatom for electrons in a chemical bond. 20. The trends for ionizationenergy, electron affinity, andelectronegativity ate the same. Theyincrease from left to right of theperiodic table and decrease down aperiod. Metals are found on the left side of theperiodic table. Nonmetals are found onthe upper right side of the periodictable. Metalloids have some propertiesof metals and nonmetals. 21. Chapter 6. Chemical Bonds.Key Concepts Chemical bonds are classified into three groups: ionsof opposite charges; covalent bonds, which result fromthe sharing of electrons by two atoms; and metallicbond, which are the attractions among positivelycharged ions for delocalized electrons. These bonds involve the valence electrons with thetendency of atoms follow the octet rule. This can berepresented by electron dot symbols or Lewissymbols. Resonance structures are used when a simple Lewisstructure is not adequate to represent a particularmolecule or ion (specie). Some covalent moleculesformed from atoms of the representation groups1, 2, and 3 lack octet configurations while atoms from5, 6, and 7 form expanded octet configurations. 22. A polar covalent bond is formed whenelectrons are not shared equally betweentwo atoms. Electronegativity difference of bondedatoms determines the kind of bondformed between the atoms. The sharing of one pair of electronsproduces a single bond, the sharing oftwo pairs, a double bond, and threepairs, a triple bond. Double and triplebonds are also called multiple bonds. 23. Chapter 7. Molecular Geometry.Key Concepts The shapes of small molecules can deexplained in terms of the VSEPR modelwhich states that electron pairs arrangethemselves as far apart as possible tominimize electrostatic repulsion. The geometry of molecules isdetermined by the arrangement ofbonding pairs and lone pairs. The five common shapes of smallmolecules are linear, trigonalplanar, tetrahedral, trigonalbipyramid, and ictahedral. 24. The electron pair cloud repulsion model suggests thatthe denser the electron clouds, the greater therepulsive force. The order from greatest to leastrepulsive force is that triple bond > double bond > lonepair > single bond (>>1.p.>). Molecules that contain polar bonds (bond dipoles) maybe polar or nonpolar molecules, depending on the shapeof the molecules. The properties of polar molecules(dipole) are different from those of nonpolarmolecules. Valence bond theory - is an extension of the Lewiscovalent bond. In this theory, bonds are formed whenneighboring atoms overlap and the potential energy ofthe system decreases. The greater the overlap, thestronger the bond formed. 25. Shapes of molecules are also described in termsof hybrid orbitals. The process of hybridizationinvolves the promotion of electron to emptyorbital(s) and mixing of the orbi