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Chapter 6.1 • What are atoms? • How are the particles that make up atoms diagrammed? • What are the similarities between covalent and ionic bonds • What are van der Waals forces? All the organisms you study in Biology are made up of matter. Atoms are the building blocks of matter. Nucleus – the dense center of the atom that contains the protons and neutrons Electron cloud – area around the nucleus where the electrons exist. An atom is mostly empty space. There are 3 basic subatomic particles. Location Charge Mass electron proton neutron Electron cloud nucleus nucleus - + neutral 0 amu 1 amu 1 amu A Boy and His Atom – IBM Bill Nye – Atoms Matter that is made up of only one kind of atom is known as an element. Elements: Pure substance – cannot be broken down into other substances Composed of only one kind of atom. ▪ Oxygen is only composed of oxygen atoms. 92 different elements occur naturally MUST know the first 40 elements! Periodic Table Game Mendeleev – discoverer of the periodic law and thus the periodic table. He arranged the periodic table looking for trends or patterns (periodic). Has been changed over time . 113 - Nihonium and symbol Nh Nihon is 1 of the2 ways to say “Japan” in Japanese Means “Land of the Rising Sun” 115 - Moscovium and symbol Mc Joint Institute for Nuclear Research, Dubna (Russia) 117 - Tennessine and symbol Ts Vanderbilt University (USA) and Lawrence Livermore National Laboratory (USA) 118 - Oganesson and symbol Og honoring a scientist and recognizes Professor Yuri Oganessian (born 1933) for his pioneering contributions. Elements are the most basic level, made up of all one type of atom. Identified by chemical symbol Organized on the Periodic Table of Elements i. ii. iii. First letter always capital Second letter (if present) always lower case Some symbols derived from Latin names: a. b. c. Sodium - Na - Natrium Iron - Fe - Ferium (blacksmiths called farriers) Lead - Pb - Plumbum (derived by a plumber) Atomic Number The number of protons in the nucleus Unique to each element Smaller # on periodic chart Protons and neutrons have a mass of 1 atomic mass unit Electrons are so small they are not counted in the mass of the atom Number of electrons equals number of protons Mass number Also referred to as atomic mass The number of protons and neutrons added together The number of neutrons in an atom can be calculated by subtracting the # of protons (atomic #) from the mass number mass # - atomic # = # of neutrons Electrons = atomic number Protons = atomic number Neutrons = mass # - atomic # Periods (Horizontal) Number of electron shells Groups (Vertical) Determine Valence Electrons Oxidation numbers: Show the number of bonds needed for full valence shell outermost electrons important in bonding. Use dots or x’s to represent valence electrons. Also called Lewis Structures – electron dot Use Group numbers (oxidation) to balance compounds +1 0 +2 +3 +/-4 -3 -2 -1 The following is the order of filling (single first, then double): 1. What is the basic unit of life? A. B. C. D. Atom Element Cells Organisms 2. How many electrons does Carbon have? A. B. C. D. 2 4 6 8 3. How is the neutron number calculated? A. Protons = neutrons B. Protons + atomic mass C. Electrons = neutrons D. Atomic mass - protons 4. Carbon and Silicon both: A. B. C. D. Have the same number of total electrons Have the same number of outer electrons Are in the same period Have the same number of protons 5. How many valence electrons does an atom of Nitrogen have? A. 3 B. 4 C. 5 D. 6 6. When oxygen forms a compound, what will happen to the electrons? A. Oxygen will Lose 2 electrons B. Oxygen will Gain 6 electrons C. Oxygen will Gain 2 electrons D. Oxygen will Lose 6 electrons Isotopes Atoms of the same element that have: same number of protons and electrons different number of neutrons Changing the number of neutrons in an atom does not affect the charge, but does affect the stability. When a nucleus breaks apart, it gives off radiation that can be detected and used for many applications. Isotopes that give off radiation are called radioactive isotopes. Carbon-11 or 11C radioactive isotope of carbon that decays to boron-11 Carbon-12 or 12C Stable, most abundant, found in living organisms Carbon-13 or 13C Stable, 2nd most abundant, used in medical diagnostic tests Carbon-14 or 14C 14C is an unstable, radioactive isotope; carbon dating Element Pure substance – cannot be broken down into other substances Mixture Two or more physically separable components Not bonded together Compound Pure substance formed when two or more different elements combine. Cannot be broken down into simpler compounds or elements by physical means but can be broken down by chemical means. Molecule Two or more atoms chemically bonded together by sharing electrons The force that holds substances together The electrons of an atom are responsible for forming chemical bonds. Electrons travel around the nucleus of an atom in areas called energy levels. Atoms become more stable by losing electrons or attracting electrons from other atoms. • When electrons are shared. • A molecule is a compound in which the atoms are held together by covalent bonds. Molecules Two or more atoms chemically bonded together by sharing electrons Diatomic molecules are all the same atom ▪ GEN – u – INE Diatomics ▪ Hydrogen, Oxygen, Nitrogen, Fluorine, Chlorine, Bromine and Iodine chlorine atom chlorine atom chlorine molecule Nonpolar: ▪ Share equally ▪ Two of the same element or in the same group Polar: ▪ Still share, but a slight charge ▪ Water ▪ Carbon with Group 6 or 7 An atom that has lost or gained one or more electrons is an ion. Ions carry an electric charge. An ionic bond is an electrical attraction between two oppositely charged atoms. Ionic Bonds: (Cation / Anion) Gain or Lose electrons Usually +1, +2 or -1, -2 (sometimes +/-3) Opposite ends of the periodic table ▪ Metals and nonmentals Cation listed first (positive charge) Anion listed second (negative charge) Some atoms tend to donate or accept electrons more easily than other atoms. • The elements identified as metals tend to donate electrons. • The elements identified as nonmetals tend to accept electrons. • Most ionic compounds • dissolve in water • are crystalline at room temperature • have higher melting points than compounds formed by covalent bonds. Series of symbols and subscript numbers that represent different chemical substances. C6H12O6 Letters represent chemical symbol of the element Numbers tell how many atoms of each element are present in the molecule Subscripts tell you the ratio of different atoms in a compound H2O • tells us there are 2 hydrogen atoms • If there is no subscript, there is just one atom. (just like coefficients in algebra) ▪ There is just one oxygen in water Parentheses are used around groups of atoms that act as one unit (polyatomic ions) Ca(OH)2 Ba(NO3)2 1) NaOH - Na is 1 because there is no subscript - O is 1 because there is no subscript - H is 1 because there is no subscript. - There are three total because of 1 + 1 + 1 = 3 2) MgCl2 - Mg is 1 because there is no subscript - Cl is 2 because that is the subscript - There are 3 total because of 1 + 2 = 3 Balance the following compound: Potassium and Oxygen A. KO B. K2O C. K2O2 D. KO2 Balance the following compound: Aluminum and Oxygen A. AlO B. Al2O C. Al2O2 D. Al2O3 Attractions between molecules. When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together. The strength of the attraction depends on: the size of the molecule its shape its ability to attract electrons. The slightly positive and slightly negative charges around the water molecule are attracted to the opposite charge of other nearby water molecules. van der Waals forces are responsible for water droplet formation and surface tension.