2/7/20121Chapter 3Atoms and Elements; Isotopes and Ions;Minerals and RocksA Review of ChemistryClicker 1Chemistry Background?A. No HS or College ChemistryB. High School ChemistryC. 1 semester College ChemistryD. 2+ semesters College ChemistryAtoms: Learning Goals•Atoms are composed of Protons, Neutrons and Electrons.•The protons and neutrons are bound into the nucleus and contain all the mass.•The electrons orbit the nucleus.•The electrons interact with neighboring atoms and determine the chemistry.Atoms•Atoms are composed of Protons, Neutrons and Electrons–A proton has an electric charge of +1 and a rest mass of 1.67 x 10-24gm. –A neutron has a charge of 0 and a rest mass of 1.67 x 10-24gm. (about the same as a proton). –An electron has a charge of -1 and a rest mass of 9.11 x 10-28gm. (much, much less than a proton).•The electron mass is negligible relative to protons and neutrons.Atoms and Elements•The chemical properties of an element depend on the number and configuration of electrons (i.e. the net electric charge). •The number of protons in the nucleus is known as the atomic number of the element. •Atomic numbers for natural elements range from 1 (hydrogen) to 92 for uranium.Atomic Number•The number of protons in the nucleus is the atomic number.•A neutral atom will have the same number of electrons as protons•The elements are arranged by chemistry into the Periodic Table.2/7/20122Ions and Valence•Atoms with 1,2, 3, or 4 outer electrons may lose them and form positive ions (cations).•Atoms with 6 or 7 outer electrons may gain electrons to form negative ions (anions).•The number of lost electrons is the valence–The valence is thus the net electric charge.•The elements are arranged by chemistry into the Periodic Table.Chemistry•The chemical reactions an element is capable of is determined by the electron configuration.•Neutral atoms with complete outer shells don’t enter chemical reactions (Inert). (He, Ne, Ar, Kr, Xe)•The number of lost electrons (net electric charge) is the valence.Ions and ValenceCharge Denoted by Superscript•Cations•H+1•Na+1•Mg+2•Al+3•Si+4•Anions•F-1•O-2•S-2Chemical Compounds•Elements occur in integer ratios to maintain charge balance•H2•H2O•SiO2•CaCO32/7/20123Atomic Number and Ions•The atomic number of an element is the number of protons (positive charges) in the nucleus.•H is atomic number 1, He 2, O 8, Ne 10 etc.•A neutral atom has the same number ofelectrons as protons.•Ions are charged atoms and have more or fewer electrons than protons.Atomic Number and Ions•Cations have fewer electrons than protons and a net positive charge.–Examples: H+, Mg2+, Al3+, Si4+•Anions have more electrons than protons and a net negative charge.–Examples: F-, O2-, Cl-•Atoms will gain or lose electrons to have a filled outer electron shell.Chemical Compounds•Elements occur in integer ratios to maintain charge balance•H2•H2O•SiO2•CaCO3Isotopes•The number of protons plus neutrons in the nucleus is known as the mass number of the atom. •Atoms of a given element (atomic number) may have differing numbers of neutrons. •Atoms of the same element with different mass numbers are known as isotopes.Mass Number•The mass numbers or isotopes of an element are denoted as precedingsuperscripts. •For example the stable isotopes of the element oxygen are denoted 18O, 17O, and 16O. •Oxygen has an atomic number of 8 (eight protons). •The nucleus of 16O thus contains eight protons and eight neutrons.Ions, isotopes, and molecules•Ions are denoted with superscripts–H+1, Na+1, Si+4, O-2•Isotopes are denoted with preceding superscripts (mass number)–2H, 3H, 14C, 16O, 18O, 90Sr, 137Cs, 235U•Molecules and compounds are denoted with subscripts–H2, O2, SiO2, CaCO3, Mg2SiO42/7/20124Atomic Weight•A given element may have several stable isotopes.•The average mass number of an element is the atomic weight.•This is not an integer.•The atomic weight of H is 1.008Nucleosynthesis• The elements H, He, and minor amounts of Li were formed in the original Big Bang.• (13.7 BILLION YEASR AGO)• All heavier elements were formed from the primordial H and He by nuclear fusionand neutron capture reactions in stars. • The fusion reaction proceeds in steps in stars massive enough to undergo the full sequence.Nucleosynthesis• Large stars undergo successive fusion reactions until Fe is formed by direct fusion.• Heavier elements are formed by neutron capture.• The final fusion stage results in a supernova explosion.• Our solar system formed from the remnants of a supernova.2/7/20125Minerals:Learning Goals•How is matter organized in the Earth?•What is a mineral?•What is A CRYSTAL? (periodic array)•How does matter self-organize?•What is a rock?•Rock cycle?Minerals•A mineral is a naturally occurring, homogeneous solid of definite chemical composition and ordered atomic arrangement that is usually formed by inorganic processes.•A Natural Crystalline PhaseIce H2OMinerals•A mineral must occur naturally.•It must be chemically homogeneous down to the atomic level•It must have a chemical formula (e.g. SiO2, FeS2)•It must have a defined crystal structure.•It must be inorganic (not the result of biological processes alone).Some Familiar Minerals•Quartz (SiO2)•Pyrite (FeS2)•Calcite (CaCO3)•Gold (Au)•Silver (Ag)•Copper (Cu)•Diamond (C)•Graphite (C)•K-feldspar (KAlSi3O8)•Na-feldspar (NaAlSi3O8)•Olivine (Mg2SiO4) •Garnet (Mg3Al2Si3O12)•Gypsum (CaSO4 2H2O)•Apatite (Ca5 (PO4)3OH)•Ice (H2O)•Halite (NaCl) (Salt)Hydrothermal Gold2/7/20126Occurrence: Evaporites, Salt DomesUses: Table salt, De-icing, Nuclear waste host rock?Halite NaCl (Salt)Calcite CaCO3Ice H2OQuartz SiO2Quartz SiO2•We often display the crystal structure of minerals as polyhedra where the corners of the polyhedra represent oxygen and center is a cation like Si4+.Mineral Properties•Hardness (Mohs Scale)•Luster•Color•Shape•Density2/7/20127Some Non-Mineral Solids•Obsidian (Glass)•Opal (Amorphous)•Coal (Amorphous)•Wood (Organic)•Amber (Organic)Which of these is not a mineral?•A. Gold•B. Diamond•C. Obsidian•D. Graphite•E. QuartzWhich of these is not a mineral?•A. Gold•B. Diamond•C.Obsidian•D. Graphite•E. QuartzPolymorphs•Same composition - different structure–Graphite - Diamond (C)–Quartz - Tridymite - Cristobalite -
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