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Ch. 5 Lecture Notes Atomic Structure and the Periodic Table 5-1 Atoms A. Early Models of the Atom 1. ____________________ – 4th century BC – world made up of empty space and tiny particles called _______________ (atomos) ‘indivisible’ a. Hypothesized _________________ using experiments B. __________________ Atomic Theory 1. All matter is made of ________________ 2. Atoms are _______________________ and cannot be __________________ into smaller particles (later proved _______________) 3. All atoms of one element are exactly _____________ (later proved wrong), but they are _____________________ from atoms of ___________ elements 4. Atoms combine in simple whole number ______________ to form _____________________ 5. In chemical reactions, atoms combine, separate, or are rearranged. 5-2 Structure of the Nuclear Atom A. Atomic Structure 1. _______________: (e-) a. Discovered by ________________ cathode-ray tube (1897) • _________________ Ray = positive and negative electrodes connected, beam travels from cathode (-) to anode (+) b. Found electrons have ______________ charge Beam in cathode ray attracted to anode (+), must be negatively charged. Relatively no ___________ (experiment by _________________ 1916) 2. _______________ – has positive charge (p+), greater __________ than an electron a. Discovered by _________________ in 1886 3. _______________ – has ______________ charge (no), _____________ in mass to proton a. Discovered by _________________ in 1932 4. ________________ = small, ________________ charged central core, made up of __________________ and neutrons a. Discovered by _____________________ gold foil experiment in 1911 b. Fired stream of positive particles at gold foil, most passed right through (atom mostly _____________ space) while a few bounced off (very _______________ positive nucleus at center) B. Development of Modern Atomic Theory 1. ___________ of conservation of matter (mass) = in a chemical reaction matter is neither created nor destroyed. a. All elements are recycled/________________!! b. Law of definite ____________________ = elements within a compound are always in certain proportions by __________ Ex: NaCl (table salt) is always 39% ______ and 61% ______. 5-3 Distinguishing between Atoms A. Atomic Number 1. __________________ = number of _________________ in the nucleus of an atom atomic # = _________ a. Determines the ______________ of the element b. Periodic table is organized by atomic _____________ c. Ex: What is the atomic number of He ______, C _____, N ______, O ______ 2. Also # of protons = # of ___________________ p+ = ________ a. Ex: How many electrons does Cl have? _______ B. Mass Number 1. ______________ = _____________ of the protons and neutrons mass # = ________________ Why do we not include electrons??? ______________ neutron = mass # - _________________ 2. Periodic Table symbols: 12 _____________________ C _____________________ 6 _____________________ C. Let’s Practice! 1. How many? Write it: Protons ____ ____ Neutrons ____ C Electrons ____ ____ 2. How many? Write it: Protons ______ ____ Neutrons ______ S Electrons ______ ____ D. Remember!!! 1. Mass # = ______________ 2. Atomic # = __________ 3. e = ________ 4. n = _______________________ E. Atomic Mass + Isotopes 1. Atomic __________ = weighted average mass of ________________ 2. __________________ = one element with __________ proton # but _________________ neutron # a. Carbon has 3 possible isotopes: 14 13 12 6 C Carbon-________, 6 C Carbon-_______, 6 C Carbon-____ F. Try it! 37 1. Ex: Isotope of Chlorine: 17 Cl p+ ______, no ______, e- ______ G. Atomic Mass Unit 1. Atomic Mass Unit (________) = 1/12 the mass of a carbon-12 atom. a. Used to ___________________ element’s masses to a standard. b. ___________ for measuring atom’s masses 5-4 The Periodic Table: Organizing the Elements A. Development of the Periodic Table 1. In 1869, ___________________ created Periodic Table of Elements a. Organized it by increasing atomic _________ and elements with similar ____________________ in same columns. b. Able to _______________ future elements properties 2. In 1913, _________________ organized it by atomic ______________. B. Modern Periodic Table 1. Organized by atomic ________________ 2. Periodic _________: grouped according to physical and chemical ______________ 3. _____________ = horizontal _________ of periodic table; numbered down the side, ______ periods 4. _____________ = vertical _________________, also called a family; _____ groups C. Group Designations 1. ______________________ elements = Group 1, 2, ____________ a. Group 1 – ________________ metals b. Group 2 – Alkaline ______________ metals c. Group 17 – __________________ d. Group 18 – ______________ gases 2. Transition _____________ = groups 3-12 D. Physical States of Elements 1. Periodic Table shows the states of the elements at ______________ temperature and normal ____________________________. a. Most are _______________________ b. Only two are ________________________ c. ____________________ elements are in the top right hand corner except for Hydrogen d. The rest are made ______________________ (man-made) through ________________ reactions (43, 61, 85, 87 and >93) E. Classifying Elements 1. ______________ - majority of elements, occupy ____________ side and center, _________________ of the staircase. 2. ______________ - occupy top ____________ hand corner (includes ______), _________ of the staircase. 3. _______________ - along the ________________ F. Metals 1. Have ______________, many _______________, conduct ___________ and electricity, usually bend w/o breaking (___________________) 2. Almost all are _______________ at room temp and have extremely high ___________________ points G. Nonmetals 1. Are abundant in ________________ a. Oxygen and Nitrogen: 99% _____________________ b. ___________________ in more compounds than all others combined! 2. _____________ conductor of heat and electricity, _______________ when solid 3. Many _____________ at room temp, __________ melting point H. Metalloids 1. Have properties of ___________ metals and nonmetals 2. ______ Metalloids: B, Si, _____, As, Sb, ____, Po (touches staircase except _____, _______) 3. Some are _______________________ = element that does not conduct electricity as well as _____________, but does conduct slightly better than _________________ a. Ex: _______________ – used in computer industry