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Unit: The Atom and The Periodic Table Slide 2 Evolution of the Structure of an Atom Slide 3 Daltons Atomic Theory All elements are composed of indivisible particles called atoms Atoms of the same element are identical. The atoms of any one element are different from those of any other element. Atoms of different elements can physically mix together or chemically combine with one another in simple whole number ratios to form compounds.(law of definite composition) Chemical rxns occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.(law of conservation of mass) Slide 4 J.J. Thomson discovered the electron plum pudding model Slide 5 Rutherford discovered the nucleus Proposed electrons surround the nucleus in a cloud Slide 6 The Atom Today The atom is the smallest particle of an element that retains the properties of that element Atoms can only be seen with proper instrumentation Daltons Atomic Theory wasnt completely correct Atoms can be broken down into subatomic particles Atoms of the same element are not identical Slide 7 Properties of Subatomic Particles Slide 8 Distinguishing Between Atoms Slide 9 Atomic Number Number of protons in the nucleus of an atom Identifies the element Elements are listed on periodic table according to atomic number Slide 10 Atomic Number Slide 11 Slide 12 atoms are electrically neutral # protons = # electrons Slide 13 Mass Number total number of protons and neutrons in an atom It is not found on the periodic table but can be estimated Slide 14 Shorthand Notation Slide 15 Fill in the following table Slide 16 Isotopes Atoms that have the same number of protons but different numbers of neutrons Differ in their mass number Slide 17 Isotopes the existence of isotopes was not predicted by Dalton, who said atoms of the same element are the same Slide 18 Isotopes identified by their mass #, write the name of the element then a hyphen with the mass number Slide 19 Isotopes Slide 20 Uses of Isotopes C-14 = archeological carbon dating Am-241 = smoke alarms I-131 = treating thyroid disorder Co 60 = cancer treatment Slide 21 Atomic Mass (atomic weight) weighted average mass of the atoms in naturally occurring samples of the element Slide 22 Atomic Mass reflects the mass and the relative abundance of isotopes as they occur in nature Slide 23 Atomic Mass To calculate the atomic mass of an element multiply the atomic mass of each isotope of the element by its relative abundance, then add the results atomic mass = mass 1 relabd. 1 + mass 2 rel.abd. 2 +... Slide 24 1. Calculate the % abundance of fictitious element Nv 2. If the mass of 293 Nv is 293.15 amu (red)and that of 295 Nv is 295.15 amu (blue), what is the atomic mass of Nv?. Slide 25 Periodic Table _______________ was the first person to find a way to list elements in order of increasing atomic mass Slide 26 Periodic Table He constructed the first periodic table in 1869, an arrangement of the elements according to similarities in their properties. Slide 27 Mendeleevs Periodic Table Slide 28 Periodic Table In 1913, ______ determined the atomic number of atoms and arranged the modern periodic table according to atomic number. Slide 29 Modern Periodic Table Slide 30 Each element is identified by its symbol placed in a square Slide 31 Modern Periodic Table The horizontal rows of the periodic table are called _____ There are ___ Slide 32 Modern Periodic Table Slide 33 Each vertical column is called a ____ or ____ There are ____. Slide 34 Modern Periodic Table Slide 35 Periodic Table A periodic law means that physical and chemical properties of elements are functions of their atomic numbers Elements in the same group on the periodic table have similar properties Slide 36 Modern Periodic Table Group A elements are called the representative elements because they have a wide range of chemical and physical properties Name the groups in Group A Slide 37 Modern Periodic Table Group B elements are called the ______________ The inner transition elements are the ______ and _____ Slide 38 Modern Periodic Table Slide 39 The representative elements can be divided into three broad classes; Metals, Nonmetals, and Metalloids What are some characteristics of each? Slide 40 Modern Periodic Table Slide 41 Niels Bohr credited for a model of the atom that states that electrons are at specific distances from the nucleus of an atom Slide 42 Bohr Models Energy Level1234 # ELECTRONS Slide 43 Bohr Models Exception: Outermost energy level can only hold up to 8e- You need to be able to diagram Bohr models for 1-36; excluding transition elements Slide 44 Bohr Models Do you notice any trends with the group or period of the periodic table? Slide 45 Bohr Models Trends: 1. Group numbers (1-8A) predict valence electrons (electrons in the outmost level). 2. The period tells you how many energy levels you have in the atom. Slide 46