Lesson 6: Periodic Table and Atomic Theory

Transcription

1 NOTES Name: _ Date: Class: Lesson 6: Periodic Table and Atomic Theory Element: fundamental substance that ; all matter consists of ~100 elements Atom: _ that can exist; smallest unit of an element that can enter into a chemical reaction Atoms are comprised of 3 SUBATOMIC PARTICLES: 1. Proton. Located in the _ of an atom. Defines the atom. Has a charge of and a mass of. 2. Neutron. Located in the _ of an atom. Stabilizes the positively-charged nucleus. Has a charge of and a mass of. 3. Electron. Located in the of an atom. Participates in. Has a charge of and a mass of. 1

2 Counting Subatomic Particles: The number of protons in the nucleus of an atom defines that atom as a particular element. Given the number of protons, identify the element: protons = protons = protons = protons = All atoms of Chlorine will have 17 protons. But the number of neutrons and electrons can vary for any atom of Chlorine. ELECTRONS: If an atom has the same number of electrons as protons, it will have a charge. For example, a neutral atom of Chlorine has protons and electrons. But, electrons are often gained or lost as atoms interact with each other. Atoms that have lost or gained electrons are called Atom loses electron(s) = Atom gains electron(s) = Valence electrons are electrons that exist in the _ electron shell. Only valence electrons are lost; when electrons are gained, they are put into the valence shell. We can predict how atoms will lose/gain electrons by their position on the Periodic Table. Groups / Families are on the Periodic Table. # of valence e s: Group #: Ion formed: 2

3 Practice: 1. During ionization, an atom of Oxygen will _ electron(s), thus becoming a(n). 2. During ionization, an atom of Calcium will _ electron(s), thus becoming a(n). 3. During ionization, an atom of Aluminum will _ electron(s), thus becoming a(n). 4. During ionization, an atom of Bromine will _ electron(s), thus becoming a (n). Trend: Metals (on the -hand side of the Periodic table) will electrons during ion formation. Nonmetals (on the -hand side of the Periodic table) will electrons. Metalloids (situated ) can either electrons. NEUTRONS Atoms of the same element that have different numbers of neutrons are called. For example, 75.78% of naturally occurring Chlorine exists as 35 Cl while 24.22% exists as 37 Cl. 35 Cl has protons and neutrons while 37 Cl has protons and neutrons. The relative abundance of these isotopes is considered in the relative atomic mass of Chlorine on the Periodic Table. The relative atomic mass is a weighted average of the masses of all naturally occurring isotopes. You can also calculate average atomic mass of a given sample. Silicon Isotope Exact mass % abundance 28 Si Si Si Copper Isotope Exact mass % abundance 63 Cu Cu

4 Ways to represent ions and isotopes: Define: Atomic number: Mass number: Atomic mass: Element Name Symbol Atomic Number (# of p) Mass Number (# of p+n) # of protons # of neutrons # of electrons Charge 27 Al Carbon 12 C Na

5 Periodic Table Organization: Columns are named by Group # and Family Name. Members within each family have similar properties. Correspond to an atom s. Used to predict. Rows are not named. Correspond to the number of that exist within an atom s electron cloud Family Names: Group 1A: _ Group 2A: _ Group 7A: _ Group 8A: _ Group B: Ion formed: Three classes of Elements: Metals, Nonmetals, and Metalloids Label each group. Then, draw the metalloid staircase and color the table to show each class of elements. 5

6 Metals, Nonmetals, Metalloids: Properties Metals: solids at room temperature (Hg is an exception), high luster, good conductors of electricity and heat, malleable, ductile, most have a high melting point and high density, easily lose electrons, low electronegativity Many metals are reactive readily chemically combine with nonmetals to form compounds. Less reactive metals can be found in a native, free state (copper, gold, silver). Metals can be mixed to form alloys (brass, bronze, steel). Nonmetals: not lustrous, relatively low melting points and densities, poor conductors of heat and electricity, high ionization energies, high electronegativities, brittle solids (not malleable or ductile), easily share or gain valence electrons, dull (not metallic) Nonmetals exist in different states solids (carbon, sulfur, iodine, phosphorous, selenium), liquid (bromine) and gases (rest of nonmetals). Nonmetals combine with other nonmetals to form molecular compounds (carbon dioxide CO 2, methane CH 4, sulfur dioxide SO 2). Fluorine is the most reactive nonmetal. Metalloids: properties that are intermediate between those of metals and nonmetals; semiconductors. Elements that Exist as Diatomic Molecules Hydrogen H 2 Oxygen O 2 Nitrogen N 2 Fluorine* F 2 Chlorine* Cl 2 Bromine* Br 2 Iodine* I 2 colorless gas colorless gas colorless gas pale yellow gas yellow-green gas reddish brown liquid bluish-black solid *Halogens very reactive References: Helmenstine, Anne Marie, Ph.D. "Nonmetals Definition and Properties." ThoughtCo, Sep. 24, 2018, thoughtco.com/nonmetals-definition-and-properties Hein, Morris and Arena, Susan. Foundations of College Chemistry Alternate 12th Edition Wiley Custom Learning Solutions. 6

7 Discovery of the Electron: Discovered by. Used a to study electric current. The glowing beam he observed was actually. Seeing a paddle wheel rotate inside the cathode tube showed that electrons have. Ernest Rutherford and the gold foil experiment The gold foil experiment revealed that the atom is comprised mostly of empty space with a dense, small positively-charged nucleus. 7

8 Want a challenge? Calculate the average atomic masses of Carbon and Silicon. How? Multiply each isotope's mass by its abundance. If your abundance is a percent, divide your answer by 100. Add these values together. 8