Chemistry Test 1 Review Basic Measurement Metric Units Length Meter m o o Mass Gram g o o Volume of Substance L Time Second s SI Units Length Meter m o o Mass Kilogram kg o o Volume of Substance cubic meter m3 Time Second s Prefixes o Kilo k 103 o Centi c 10 2 o Milli m 10 3 o 1 mL 1 cm3 Rule Read one more digit than that marked on the instrument Significant Figures Last sig fig is always the estimated digit o o As long as there is a decimal count the first nonzero number and everything after o o o Multiplication and Division a calculated quantity contains no more significant figures that the least number Trailing zeros do NOT count Exact numbers contain an infinite number of sig figs counted and defined quantities are exact of sig figs in the data used in the calculation o Addition and Subtraction calculated quantity should have the same number of decimal places as the measurement with the least number of decimal places Scientific Notation o o o In addition and subtraction you must have the same exponent In multiplication multiply the numbers and add the exponents In division divide the numbers and subtract the exponents top bottom Heat Energy Transfer at the Molecular Level Temperature is the measure of kinetic energy o Hot Fast Molecules o Cold Slow Molecules Temperature o o Kelvin Celsius Fahrenheit o F 1 8C 32 o K C 273 15 Density o D m v o Chemistry o A study of Common units g cm3 g mL or g L The composition structure and properties of matter The physical and chemical transformations of matter The energy associated with such transformations Matter o Has mass o Occupies Space o o Undergoes physical and chemical changes Characterized by physical and chemical properties Different States of Matter Classification of Matter Law Governing Behavior of Matter Law of Definite Proportions Law of Constant Composition Different samples of any pure compound contain the same elements in the same proportion by mass Atoms Democritus 2400 years ago o Greek Philosopher o o o Could matter be divided into smaller and smaller pieces forever or was there a limit to the number of times a piece of matter could be divided Theory matter could not be divided into smaller and smaller pieced forever eventually the smallest possible piece would be obtained This piece would be invisible o Atomos not to be cut o To Democritus atoms were small hard particles that were all made of the same material but were different shapes and sizes o Atoms were infinite in number always moving and capable of joining together Aristotle Timeline of Atomic Theory o Rejected atoms o He and Plato favored the belief in 4 types of matter earth fire air and water THEY WERE WRONG o His work led to the acceptance of the idea of atoms and changed the way symbols were used Symbols now for John Dalton elements not words Father of Modern Chemical Theory o o Dalton s Theory 1803 All matter composed of atoms Atoms are indivisible and indestructible particles FALSE Atoms of the same element are exactly alike and differ from those of other elements Compounds are formed by the joining of atoms of two or more elements A given compound always has the same number and type of atoms o o o o o o Atoms are not created or destroyed only rearranges in chemical reactions Elements 114 made or predicted 1 92 are natural except Tc Fr Pm and At 88 naturally occurring 93 and above are synthetic o o o o Need to know 1 36 Ag Pt Au Hg Sn Pb I Rn U Nuclear Evidence o Joseph John Thomson Described cathode rays Cathode rays are radiation produced from high voltage through partially evacuated tubes These rays traveled in straight lines but were attracted to the positive poles of electricity and magnets indicating the rays are negative When a small paddle wheel was placed in the path of cathode rays the wheel was set in motion The rays were thought to be composed of negative particles that were called corpuscles later electrons Conclusion All metals and gases and probably all atoms contain electrons But atoms are neutral so atoms must contain positive charges to balance the negative charges of the electrons Thomson was never able to find the positive particles In 1897 Thomson measured the electrical charge to mass ration of an electron Electrons were thought to be embedded in a positively charged ball of matter This is the plum pudding or Thomson model Robert A Milliken Ernest Rutherford o Did an experiment in 1909 to determine the charge of an electron then calculated the mass o Made the plum pudding model obsolete o The experiment was to direct a beam of positively charged particles at a thin piece of gold foil Around the foil was a screen coated with zinc sulfide which gave flashes of light when the particles struck it Structure of the Atom For positive particles to be deflected there must be a heavy positive object in the atoms of gold with mostly open space o By 1911 we had the nuclear atom or Rutherford The nucleus was thought to be small dense heavy positive and surrounded by electrons The Rutherford model of the atom was abandoned because an observation was made in the lab that his model couldn t explain If Rutherford s model was correct the electrons should be continuously emitting energy of all wavelengths resulting in a continuous spectrum of electromagnetic radiation white light o Discovered that the nucleus also contained neutral particles Neutrons had no charge but were slightly more James Chadwick massive than protons Composition o Atoms of the same element have the same number of protons The number of protons is called the atomic number The number of protons equals the number of electrons in a neutral atom this is he same as the atomic number o Nucleus takes up very little space in the atom o The mass of an atom depends on the protons and neutrons Protons Neutrons Mass Number Isotopes have the same atomic number but different mass numbers same number of protons different number of neutrons o Atomic mass is the weighted average of the masses of naturally occurring isotopes Ions are produced when an atom loses or gains electrons Isotopes Atomic Mass Ions o Atoms Bohr Structure o Arranged by periodic number o Group or Family vertical columns of elements with similar chemical and physical properties o Period horizontal rows of elements whose properties change progressively Family Names o Group 1A Alkali Metals o Group 2A Alkaline Earth Metals o Group 1 10 B Transition Metals o Group 7A Halogens o Group 8A Noble Gases Physical Properties of Metals
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