Atoms and Molecules

Atoms and Molecules The Composition of Elements: Define atom: The smallest unit that has the properties of an element Dalton’s Atomic Theory: There are four parts to ___Dalton___’s atomic theory: 1. All matter consists of small particles called ___atoms____ 2. All atoms of the _same____ element are __alike ___, but differ in their properties from atoms of other elements. 3. __chemical___ reactions take place between atoms, and the atoms never___break___ into pieces. 4. Atoms __combine____ with other atoms to form __molecules_____. Protons, Neutrons, and Electrons: The electron is an extremely small, very lightweight particle that has a _negative___ electrical charge. _protons____ are much heavier than electrons and have a _ positive__ charge. __neutrons___ have no charge at all – they are neutral. The protons and neutrons are located at the ___nucleus_____ (the center of the atom). The electrons orbit the nucleus of the copper atom in several layers called _shells______________________ (also sometimes called energy levels). Any substance in which electrons can move freely is called a ____conductor____. The first shell needs a total of __ 2___ electrons to be complete. The second shell can contain a maximum of ____8__ electrons. The third shell can contain a maximum of eighteen electrons, although in some instances _____8____ electrons will form a complete shell (and for our purposes, 8 is a complete third shell!) What does it mean to be electrically neutral? The number of negative charges is balanced by an equal number of positive charges. Atomic Structure of the Elements: The __ atomic number _ of an element tells us the number of protons an atom has. We can also safely assume that it is the number of __electrons__ that an element has as well. An atom whose outermost shell isn’t complete tends to __borrow___ or lend__ electrons until that shell is complete and a __stable__ condition is reached. Define noble gasses: elements in the last group, with full outermost shells. They are stable. Atomic Mass: The values representing atomic masses are pure numbers; they aren’t expressed with any measuring __units__ because they indicate the ratio of the mass of an element to ____carbon__-_12_ Molecular Mass: The molecular mass of a compound is the ___sum_____ of the __atomic___ ___masses______of all the individual atoms in one molecule of the compound. The Classification of Matter Chemistry: Define Chemistry: Study of the composition of the substances around us and ways in which they can be changed into other substances. Matter: Define matter: anything that has mass and takes up space _Substance_____ means a particular kind of matter. A _Solid____ substance holds its shape without outside restraint; the shape and volume are fixed (fixed means it does not change) . A __liquid___ substance is one that has no shape of its own, but has a definite fixed volume. A _gaseous__ substance is one that has no definite shape or volume and that will expand indefinitely if not restrained. A __physical___ property is one that is displayed without any change in composition (ex., color, mass and luster). A __ chemical ______ ____Property___ of a substance is how it’s makeup is altered when it undergoes a chemical change or reaction. Physical and Chemical Changes of Matter: A change in the form of a substance without the production of a new substance is called a __physical____ change_______. A chemical change occurs when the ___composition___ of a given substance changes so that the substance no longer exists in its original form and a _new__ __substance__ is produced. Chemical classifications of matter: A chemical ___element___ is a substance that can’t be broken down into simpler forms by chemical change. A compound consists of two or more __ elements___ that are __combined __ chemically in such a way that the elements themselves can no longer be identified by their__individual_____ __properties___. In a ___mixture___ , two elements are mingled together without combining chemically. The materials keep their ________Individual_____ ___properties____________. The Elements: Approximately _____118_____ elements have been discovered and identified. (It says approximately because scientists keep finding new ones, so that number could increase!) The ___chemical symbol _______ is usually the first letter or two of the element’s name (but not always) *See the periodic table or table 1 for the chemical symbols of all elements* Compounds Compounds are formed when two or more elements __________ _________________. In the example of table salt… two ____________________ that are very _____________separately may be combined to form a compound that’s essential to human life. All the distinctive _______________ of the elements making up this salt have been__________ in the compound. Mixtures A ___mixture___ is composed of two or more elements or compounds that ____don’t___ chemically combine on contact. The ingredients in a mixture can be ____separated__ without requiring chemical change. The Periodic Table of Elements, Part 1 Early Developments: In 1869, a Russian chemist named __Mendeleev_____published a table of the elements arranged according to increasing atomic __masses___. Define periods: horizontal rows on the table Define groups: vertical columns on the table Elements in the same ___ group_____ tend to share very similar properties. Note that groups are labeled 1-18 across the top of the periodic table. The Noble Gases: All of the noble gases (group 18) have the ___ maximum ______ number of ___ electrons ____ possible in their outer shells, making them stable. Therefore, they don’t form ___compounds_____. The Halogens: The ___halogens_______ are five nonmetallic elements located in group 17. They have 7 valence electrons and are very chemically active. Fluorine is the most _____ active____ of all of the chemical elements. The Fundamental Laws of Chemistry and Valence The Law of Conservation of Matter: The law of __conservation__ of matter states that matter can neither be __created___ nor __destroyed____ by chemical means, but it can be _ changed__ from one form to another. The Law of Conservation of Energy: The law of ___ conservation___ of _energy__ states that energy, can neither be created nor destroyed in chemical reactions, only changed from one form to another. Nuclear Energy and the Conservation Laws: Energy given off as the result of atomic disintegration is called __nuclear_____ energy. Matter can be converted to energy only in a nuclear reaction. The Law of Definite Proportions: The law of __definite___ __proportions____ states that the composition of a chemical compound never varies. Valence: Valence is defined as the number of ____electrons_______ that an atom must ___borrow______or _lend____ to complete its outermost shell. Chlorine needs to borrow one more electron to fill its outermost shell…we simply say that chlorine has a valence of ___ -1__. The outermost shell of the sodium atom contains one valence electron that it needs to give away…. Thus, we say that sodium has a valence of ___ +1____. Define Valence electrons: electrons in the outermost ring – they may be borrowed or lent. Valences of metals and non-metals: The electron theory makes it possible to define metallic elements as __lenders___ of electrons. In the atoms of metallic elements, the outermost shell contains _less_____ ___than____ ____half__ the number of electrons required to complete it. If the outermost shell of an atom contains half the number of electrons necessary to complete the shell, it may either borrow or lend electrons… this atom is said to be ____amphoteric____. Chemical Activity Related to Valence: The __chemical___ ___activity____ of an element is directly dependent on the tendency of the atom of that element to form a ___full___ the chemical activity of the element. ___outer___ _____shell___; the greater this tendency, the greater Generally speaking, the ___greater____ the number of electrons an atom has to ___borrow__ or to __lend_, the ____less___ the activity of that atom. Chemical Unions: Define chemical union: atoms of different elements combine to form a compound. The two opposing electrical charges must ____balance____ one another. The Periodic Table of Elements, Part 2 The Nonmetals: Hydrogen is a colorless odorless, and tasteless ___gas____. Its ___mass_____ is less than that of any other element; it’s the ____lightest____ substance known. Carbon exists in nature in three forms. In two of these forms, __diamond___and _graphite___, the carbon has a crystalline structure… Amorphous carbon is an important constituent of ___coal___, coke, and charcoal. Nitrogen makes up nearly ___four____-__fifths___ of the volume of the air. The Periodic Table of Elements, Part 3 When oxygen combines with elements, the reaction is called ___oxidizing_____. If the combining rate is very rapid, heat may be given off to such an extent that _____burning______occurs. (We also say it undergoes combustion) _Phosphorus_____(P) has such a strong affinity for oxygen and other elements that it never occurs free in nature. In its usual form, sulfur (S) is a brittle, crystalline _solid____that’s __lemon-yellow_____ in color. In metallic form, it Selenium conducts ________electricity______ to some extent Water, the Most Common Liquid Compound Purifying Water: In the __ aeration____ method, water is sprayed into the air so that sunlight and oxygen may kill most of the bacteria present. In the ____filtration____ method, water is passed through a filter (usually sand) to remove impurities. In the ____chlorination________ method, the chemical chlorine is used to destroy bacteria. In the ___coagulation___ method, special chemicals are added to water, causing bacteria to settle out of the water. The Earth’s Atmosphere: Air is a mixture of gases. The average composition of dry air by volume is as follows: _nitrogen_____ 78%; __oxygen__ 21%; __carbon dioxide___ 0.04%; The Metallic Elements The Alkali metals: The alkali metals are very ___ reactive_____ metals …. they’re found in group _1__ of the Periodic Table of Elements. Some alkali metals can ______explode__________ if they’re exposed to water. Alkaline Earth metals: Alkaline earth metals are ___metallic____ elements found in Group __2_ of the Periodic Table. The Other Metals: Aluminum, gallium, indium, tin, thallium, lead, and bismuth … are __solid___, have relatively high ____densities___, are opaque, and are ductile and _____malleable____. Transition Metals: The ___ valence___ electrons of transition metals are present in more than one _shell_. Three elements in the transition metals family—___ iron_______________, _____cobalt____________, and __nickel___ - are the only elements known to produce __magnetic_______ fields. The Metalloids: The metalloids are elements that have some properties of both ___metals____ and ___nonmetals____. The Rare Earth Elements: The rare earth elements are composed of the ___lanthanide______ series and the __actinide______ series. All the members of the actinide series are __radioactive_____ metallic elements. Ions The Conductivity of Solutions: An ___ion____ is an atom or a radical that has either gained or lost one or more electrons (and now has a charge). Define anion: negative ion Define cation: positive ion Symbols for Ions: ____ionization____ is when a molecule dissociates (meaning, splits apart) into a positive ion and a negative ion. (For example, NaCl into Na+ and Cl- ) Substances that dissociate to a large degree are good conductors of electricity are called _____electrolytes____ Acids and the Theory of Ionization Free hydrogen ions that impart the ___sour___ taste to water solutions of acids, that neutralize ___bases_____, and that turn litmus paper _____red______. Bases and the Theory of Ionization Free hydroxyl ions in basic solutions that are responsible for turning pink litmus paper ___blue_____and for giving bases their characteristic “___soapy___” feeling. The pH Scale: The degree of acidity or alkalinity is expressed in _pH___ values. Electrolysis: Define electrolysis: The chemical change caused by conducting a current through an electrolyte The cathode is the ___negatively______ charged electrode, and the anode is the ___positively____ charged electrode in electrolysis Electroplating: In electroplating, a ___metal______ is deposited on the electrode surface. Metals, Nonmetals, Acids, Bases, Salts Metals: Metals have a characteristic ___luster______, conduct _heat____ and ___electricity____, are ___malleable____ and ductile and form stable compounds with acids. Another characteristic of metals is that they replace the __hydrogen____ of acids. Strongly active metals replace the __ hydrogen_____ in water, forming __hydroxides_____. Extracting metals from ores and refining them is called ____________________________. The corrosion of metals is caused by the slow _____ combination____ of the metals with __oxygen____, water __vapor___ and _________carbon dioxide in the air. To prevent the corrosion of iron… the exclusion of air and moisture can be accomplished by ____Painting______, oiling, or enameling the iron, by galvanizing it with zinc, or by plating it with a ___metal__such as copper, nickel, or tin. Nonmetals: Metals are often called ___positive__ elements, and nonmetals ____negative___ elements. This is because metals show a positive charge and nonmetals a negative charge when electric __current____ is passed through a solution containing them. Define metalloids: elements that have characteristics of both metals and nonmetals. The electrochemical series: The electrochemical series compares the activity of different metals (and hydrogen). Any metal in the list is replaced from its compounds by any metal _ above______ it, but replaces any metal _____below_____it. Those at the __ top___ of the list are so active they are never found free (meaning they combine with other atoms so easily that they are never found all by themselves in nature). The activity indicated by the series …. applies to the relative effectiveness of the metals in displacing the __hydrogen____ of acids. Acids: An acid is a substance that contains ___hydrogen_____ that may be replaced by a___metal_____. Acids in water break apart and release _H+__ ions. Bases: Bases in water break apart and form an __-OH_____ion. Alkali is a word for a strong ____ Base____ (and “alkaline” is an adjective to describe that type of solution). Salts: A __salt___ is the product formed by a reaction in which the hydrogen atoms of an acid are replaced by the atoms of a metal. Salts are prepared by treating a ____________ with an ____________. Chemical Formulas and Names What is a formula: Define formula: a group of standardized symbols used to express the composition of a substance The symbol for the metallic element is always written _first__ in a formula. Small numbers called __subscripts___ are used to indicate the number of each atom that’s needed in the compound. Valences in Formulas: A compound is electrically neutral; the ___positive___ valence charges ___balance______ the _______negative_______ valence charges. Rules for writing formulas for compounds: • First write the symbol for the __positive______ element (the metal, with a positive valence). Then write the symbol • • Place the valence of the elements involved __above____ and to the _right___of the symbols for the elements. (See Table 2 for valences) After the second element in the formula, place as the subscript the number of __positive___ charges indicated over • After the first element in the formula, place as the subscript the number of __negative___ charges over the second for the ______negative_______ element. the first element element. This balances the formula. Radicals: Groups of different atoms will join together and act as a single unit when forming __compounds_____. Such a group of atoms is called a __radical_____. The Names of Elements and Compounds: Generally, the names of metallic elements end in the suffix ___-ium____. The suffix –ide usually indicates a compound made up of ___two___ elements (or sometimes one element and one radical). The suffixes –ate and –ite indicate that there are more than two elements in the compound, and one of them is ___oxygen_______. The suffixes –ous and –ic indicate the ___valence______ of a ___metal_____. Chemical Equations Equations, the Expressions of Chemical Changes: Label the “reactants” and the “products” in the sample equation: Balancing Equations: An _equal___ number of atoms must appear on each __side__ of the chemical equation. A _____coefficient_________ is a number placed in front of a chemical symbol to show the number of atoms or molecules involved. The five general types of chemical reactions: In a __combination ___ reaction, two or more substances undergo a chemical union to form a more complex substance In a __decomposition___ reaction, compounds break up into simpler constituents. In a __substitution___ reaction a free element replaces another element in a compound. In a __double replacement___ reaction, two elements or radicals change places with two other elements or radicals In a __reversible____ reaction, the products react with each other to re-form the original substances. Calculations in Chemistry – Molar Mass Calculating Molecular Masses from Chemical Formulas: There are four steps that can be used to calculate the molecular mass of any compound from its formula: Step 1: Break the compound down into its individual ___elements______. Step 2: Find the atomic mass of each element from the atomic mass table. Step 3: Multiply the atomic mass by the _________subscript___________ to get the total mass of the elements Step 4: Find the ___sum_____ of the masses of all the elements present. This is the molecular mass. Calculating the Percentage Composition of a Compound from its Formula To determine the percentage composition of a compound from its formula, use the following Steps: Step 1 : Calculate the ___molecular mass________ of the compound Step 2: Divide the ____ atomic _ ___mass___ of each element (multiply them by the subscripts first, if there are any!) by the __molecular mass____ of the compound. Step 3: Convert the answers to percentages by multiplying each one by _100_____. Energy and Reaction Rates in Chemistry Chemical Reactions and Energy: All chemical reactions either _______________ or __________________ energy from their surroundings. Chemists call reactions that release heat ____________________________ reactions. ____________________________ reactions are chemical reactions that absorb heat. Reaction Rates: List the 4 ways to increase reaction rates: Nuclear Energy Natural Radioactivity: In the disintegration process, elements give off radiation, so elements that disintegrate are called _radioactive___ elements. ____alpha_____ rays are the nuclei of helium atoms with a +2 electric charge, __beta____ rays are high-speed electrons, and __gamma___ rays are similar to X-rays but shorter in wavelength. It takes a certain amount of time for half of the atoms present in any particular mass of radium (or any radioisotope) to decompose. This period is called the __ half life_______ of the element. The Uses of Nuclear Energy: Since World War II… scientists have developed many ______________ uses for nuclear energy. Artificial Disintegration: Scientists have found that certain normally ___________ atoms can be caused to disintegrate by __________________ them with rays or particles. Artificial Radioactivity: By the bombardment process, radioactive elements called radioactive isotopes or ___radioisotopes_____ can be prepared. In the field of medicine, __radioactive_____ __isotopes_ provide useful _treatments______ for a variety of diseases, including certain ______cancers __. ____Radiophosphorus____ is used to study fertilizer absorption, which is essential to plant nutrition. Industry also uses radioisotopes as ____tracers ____ to find _flaws___ in castings and measure the ___thickness__ of paper, rubber, and plastic products. Nuclear Fission: In nuclear ____fission______ the splitting of atoms does occur. In fission, the lost mass is converted into _heat__ and _light____ energy. Nuclear Reactors: Nuclear ___reactors___ provide the means to control the chain reaction. Power Reactors: Several reactors have been designed primarily to produce ___electricity____. In a pressurized-water, graphite-moderated reactor shielded by concrete…ordinary water at a high ___pressure___ is heated by circulating it through a ______reactor_____. The fuel for this reactor consists of __uranium 238______ enriched with ___uranium-235_________. (Note: all of the types of power reactors described use the nuclear energy simply to heat steam! The steam is used to power a turbine and make electricity.) up water to make Detecting and Measuring Radiation: A simple instrument for measuring the intensity of radioactivity is the __Geiger_ counter. The Fusion Process: ___ Fusion__ is a nuclear reaction in which light elements are combined into a heavier element with a resultant release of great amounts of energy. Controlled Fusion Power: A controlled-fusion power reactor is most desirable because no ___radioactive__ would result, and because there’s an abundant supply of fuel in ordinary water. ___waste__ materials The problem of fusion power isn’t merely how to start and control a fusion reaction, but how to __confine ____ it. How can a gas at extremely high __temperature___ and __pressure___ be confined within a chamber without destroying the chamber? Finding the answers is the focus of ____international_____ scientific effort. Organic Chemistry ___Organic____ chemistry is defined as the chemistry of compounds containing carbon. Structural Formulas: The _______ Arrangement _________ of elements affects the ____characteristics_______and ______behavior__________ of a compound. ______Structural_______ formulas are used as a kind of shorthand to indicate the molecular arrangement Hydrocarbons: __Hydrocarbons_____ are compounds composed of carbon and hydrogen only. _Aromatic___ carbons have a ring structural formula Paraffins: _________Paraffin hydrocarbons ____ also called ___alkenes___ have the general formula CnH2n+2 there are 3 carbons, there are 2x3+2 Hydrogens; C 3H8 ) (meaning if List 3 products of crude petroleum/crude oil: Gasoline, kerosene, asphalt, oils, greases, and paraffin wax Olefins: The ____olefins__ , which are also referred to as _alkenes____, are hydrocarbons in which two or more carbon atoms are joined by _ double_____ bonds. The general formula for the series is CnH2n. (meaning if there are 3 carbons, there are 2x3 hydrogens; C3H6). Acetylenes: The ___ acetylene ___ (also called Alkynes) hydrocarbons contain triple bonds. The general formula for the series is CnH2n-2 (meaning if there are 3 carbons, there are 2x3-2 hydrogens; C3H4). Alcohols: __alcohols___ are organic molecules containing a hydroxyl (OH) group. Alcohols are obtained by replacing one or more of the _hydrogen___ atoms in a paraffin by the same number of ____OH ___ radicals. Aldehydes: When an alcohol is oxidized…it forms a compound called an __ aldehyde___. A typical reaction is: Ketones: A secondary alcohol will react with an oxygen to form a _ketone_____. Ethers: __Ethers__ are derived from alcohols by substituting a radical for the hydrogen in the hydroxyl (OH) radical. (The O stays, but the H is replaced with a different group). Carbohydrates In Carbohydrates, the proportions of __hydrogen____ and ___oxygen____ are the same as in water. Plastics: The production of synthetic plastics involves a process known as _polymerization_____ in which many molecules of a simple carbon compound are linked together. The simple starting carbon compound involved in polymerization is called the ___monomer_____, and the product of the polymerization reaction is called the ____polymer____. The Classification of Plastics: A __thermoplastic____ material softens on heating and becomes rigid on cooling. Reheating will soften the material. A ___thermosetting_______ material also softens on heating but sets (cures) under further heating to form a hard product. Medicinals: ___analgesics_______ are drugs that are used to reduce pain. ____ sulfanomides ________ are drugs that prevent the growth of bacteria in body systems. ____ antibiotics ______ are chemicals of natural origin that can kill or inhibit the growth of microorganism s. _______ hormones ________ are compounds secreted by the endocrine glands of the body that help regulate body functions. _______ tranquilizers ___________ or psychic depressants, are used to treat a wide variety of mental disorders. Synthetic Fibers: __synthetic fibers__ or manmade textile fibers have revolutionized the textile industry. These fibers are usually long-chain ___ polymers______. List four examples of synthetic fibers: Rayon, Cellulose Acetate, Orlon, Daycron