* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download chapter2 2012 (no naming) 2014
Inorganic chemistry wikipedia , lookup
Livermorium wikipedia , lookup
Condensed matter physics wikipedia , lookup
Nuclear binding energy wikipedia , lookup
Particle-size distribution wikipedia , lookup
Inductively coupled plasma mass spectrometry wikipedia , lookup
Coordination complex wikipedia , lookup
Abundance of the chemical elements wikipedia , lookup
Resonance (chemistry) wikipedia , lookup
Electronegativity wikipedia , lookup
Atomic orbital wikipedia , lookup
Electric charge wikipedia , lookup
Hypervalent molecule wikipedia , lookup
Metastable inner-shell molecular state wikipedia , lookup
Isotopic labeling wikipedia , lookup
Gas chromatography–mass spectrometry wikipedia , lookup
Nuclear transmutation wikipedia , lookup
Chemical element wikipedia , lookup
Molecular dynamics wikipedia , lookup
Periodic table wikipedia , lookup
Metallic bonding wikipedia , lookup
Geiger–Marsden experiment wikipedia , lookup
Elementary particle wikipedia , lookup
Electron configuration wikipedia , lookup
History of chemistry wikipedia , lookup
Extended periodic table wikipedia , lookup
Chemical bond wikipedia , lookup
Rutherford backscattering spectrometry wikipedia , lookup
IUPAC nomenclature of inorganic chemistry 2005 wikipedia , lookup
Chemistry: A Volatile History wikipedia , lookup
Atomic nucleus wikipedia , lookup
Unit #2 Atoms, Molecules and Ions Introduction • Atoms • Composed of electrons, protons and neutrons • Molecules • Combinations of atoms • Ions • Charged particles Greeks: Empedocles and Democritus • Suggested the concept of atoms but were not taken seriously or credited with an atomic theory John Dalton: credited with the first atomic model Figure 2.1 - John Dalton and Atomic Theory Atomic Theory 1. An element is composed of tiny particles called atoms 2. All atoms of the same element have the same chemical properties 3. In an ordinary chemical reaction, atoms rearrange their bonds but atoms are not created or destroyed 4. Compounds are formed when two or more atoms of different element combine Fundamental Laws of Matter Law of Conservation of Mass Matter is conserved in chemical reactions This applies to all chemical reactions but DOES NOT include nuclear reactions Law of Constant Composition Compound always contains the same elements in the same proportions by mass. Pure water has the same composition everywhere. Law of Multiple Proportions • The masses of one element that combine with a fixed mass of the second element are in a ratio of small whole numbers. Compare CO and CO2 Figure A – The Law of Multiple Proportions Two different oxides of chromium Components of the Atom • Atomic theory raised more questions than it answered • Could atoms be broken down into smaller particles • 100 years after atomic theory was proposed, the answers were provided by experiment • Finding the Electrons: Protons: Neutrons: J.J. Thomson • Discovered the electron Figure 2.2 – J.J. Thomson and Ernest Rutherford Figure 2.3 – Cathode Ray Apparatus • Apparatus used by Thomson to show existence of electrons Electrons • First evidence for subatomic particles • J.J. Thomson in 1897 • Rays emitted were called cathode rays • Rays are composed of negatively charged particles called electrons • Electrons carry unit negative charge (-1) and have a very small mass (1/2000 the lightest atomic mass) J.J. Thomson’s Model – “Plum Pudding Model” • Every atom has at least one electron • Atoms are known that have one hundred or more electrons • There is one electron for each positive charge in an atom • Electrical neutrality is maintained Ernest Rutherford: Discovered the nucleus of the atom Gold Foil Experiment: • Bombardment of gold foil with α particles (helium atoms minus their electrons) • Expected to see the particles pass through the foil • Found that some of the alpha particles were deflected by the foil • Led to the discovery of a region of heavy mass at the center of the atom = nucleus Figure 2.4 – Rutherford Backscattering Nuclear Particles 1. Protons • Mass nearly equal to the H atom • Positive charge 2. Neutrons • Mass slightly greater than that of the proton • No charge Atomic Mass • The average mass of all of the isotopes of an element accounting for their relative abundances Table 2.1 – Subatomic Particles Terminology • Atomic number (a#) lower left • Number of protons in the atom • Mass number (m#) upper left • Number of protons plus number of neutrons • Mass # = p+ + n0 Nuclear symbolism Mass Number Chemical symbol Atomic Number Isotopes • Two or more atoms of the same element (same atomic number) but with different numbers of neutrons and mass numbers • Relationships: • Atomic number = # p+ • Charge = p+ - e• Mass # = p+ + n0 Example 2.1 Radioactivity • Radioactive isotopes are unstable (Radioactive decay is not a chemical process) 1. These isotopes decay over time 2. Emit other particles and are transformed into other elements • Particles emitted 1. Beta (β) particles: High speed electrons 2. Alpha (α) particles: helium nuclei 3. Gamma (γ) rays: high energy light Nuclear Stability • depends on the neutron/proton ratio • For light elements, n/p is approximately 1/1 • For heavier elements, n/p is approximately 1.4/1 Figure 2.5 – The Nuclear Belt of Stability Introduction to the Periodic Table • Dmitri Mendeleev: 1836-1907 • Arranged elements by chemical properties • Left space for elements unknown at the time • Predicted detailed properties for several undiscovered elements: • Sc, Ga, Ge • By 1886, all these elements had been discovered, and with properties similar to those he predicted Mendeleev’s P.T. Introduction to the Periodic Table Modern Periodic Table • Period – a horizontal row on the periodic table • Group – a vertical column on the periodic table • Blocks – sections of elements with common properties • Families – another name for group; emphasizes the similarity in properties within a group Blocks in the Periodic Table • Main group elements • 1-2, 13-18 OR roman numeral +A groups • Transition Metals • 3-12 OR non roman numeral groups • Inner Transition/Rare Earth elements • Bottom double rows Families with Common Names (label on PT) • • • • Alkali Metals, Group 1(I) Alkaline Earth Metals, Group 2 (II) Halogens, Group 17 (VII) Noble Gases, Group 18 (VIII) Example 2.3 Molecules and Ions • Molecule: Two or more atoms chemically combined 1. Atoms involved are often nonmetals 2. Covalent bonds are strong forces that hold the atoms together • Molecular formulas: • Number of each atom is indicated by a subscript • Examples • Water, H2O • Ammonia, NH3 Structural Formulas • Structural formulas: a formulas that shows the bonding patterns within the molecule Ions • A charged particle that is the result of the loss or gain of electrons • Cation – a positive ion (loss) • Anion – a negative ion (gain) • Examples: • Na → Na+ + e• O + 2e- → O2- Ionic Compounds • Compounds formed from the electrostatic attraction of oppositely charged particles • Sodium chloride (NaCl): Sodium cations and chloride anions associate into a continuous network Forces: • Ionic compounds are held together by strong forces • Compounds are usually solids at room temperature • High melting points • often water-soluble Solutions: • When an ionic compound dissolves in water, the ions are released from each other • conductivity – the ions in a solution support the transmission of an electric current • Strong electrolytes – solutions that are very good conductors • Weak electrolytes – solutions that are poor conductors • Nonelectrolytes – solutions that do NOT conduct Figure 2.12 – Electrical Conductivity Formulas for Ionic Compounds • Charge balance • Each positive charge must have a negative charge to balance it • Calcium chloride, CaCl2 • Ca2+ • Two Cl- ions are required for charge balance Transition Metals • Polyvalent – exhibit multiple positive charges depending on conditions • Iron forms Fe2+ and Fe3+ • Lead forms Pb2+ and Pb4+ Polyatomic Ions • Groups of atoms may carry a charge; these are the polyatomic ions • OH• NH4+ Noble Gas Connections • Atoms that are close to a noble gas (group 18 or VIII) form ions that contain the same number of electrons as the neighboring noble gas atom • +1, +2, +3 skip -3, -2, -1 Noble Gases