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Subatomic particles Electron Proton Neutron NameSymbolCharge Relative mass Actual mass (g) e-e- p+p+ n0n0 +1 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10 -24
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Counting the Pieces Atomic Number = number of protons in the nucleus # of protons determines kind of atom The same as the number of electrons in the neutral atom. Mass Number = the number of protons + neutrons. These account for most of mass
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Counting the Pieces Protons: equal to atomic number Neutrons: Mass Number – Atomic Number Electrons: In a neutral atom equal to atomic number
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Symbols Contain the symbol of the element, the mass number and the atomic number.
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Symbols Contain the symbol of the element, the mass number and the atomic number. X Mass number Atomic number
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Symbols Find the number of protons number of neutrons number of electrons Atomic number Mass Number F 19 9
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Symbols n Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass Number Br 80 35
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Symbols n if an element has an atomic number of 34 and a mass number of 78 what is the –number of protons –number of neutrons –number of electrons –Complete symbol
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Symbols n if an element has 91 protons and 140 neutrons what is the –Atomic number –Mass number –number of electrons –Complete symbol
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What if Atoms Aren’t Neutral Ions: charged atoms resulting from the loss or gain of electrons
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What if Atoms Aren’t Neutral Anion: negatively charged ion; result from gaining electrons Take the number of electrons in a neutral atom and add the absolute value of the charge 81 35 Br 1- Identify: Number of Protons Number of Neutrons Number of Electrons
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What if Atoms Aren’t Neutral Cation: positively charged ion; result from the loss of electrons Take the number of electrons in a neutral atom and subtract the value of the charge 27 13 Al 3+ Identify: Number of Protons Number of Neutrons Number of Electrons
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Isotopes Atoms of the same element can have different numbers of neutrons Different mass numbers Called isotopes
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Naming Isotopes We can also put the mass number after the name of the element. carbon- 12 carbon -14 uranium-235
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Atomic Mass How heavy is an atom of oxygen? There are different kinds of oxygen atoms We are more concerned with average atomic mass Average atomic mass is based on abundance of each element in nature. We don’t use grams because the numbers would be too small
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Measuring Atomic Mass Unit is the Atomic Mass Unit (amu) It is one twelfth the mass of a carbon- 12 atom Each isotope has its own atomic mass, thus we determine the average from percent abundance
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Atomic Mass Is not a whole number because it is an average. are the decimal numbers on the periodic table.
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Modern Periodic Table The modern periodic table consists of Rows and Columns Rows - Horizontal Also known as Periods Numbered 1-7 Columns - Vertical Also known as Groups and Families Numbered 1-18
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Metals The most common class of elements is Metals Metals become cations What is a cation? How are they formed? Positively charged atom - Lose electrons Metals are generally solid (except Hg), conductive of heat and electricity, malleable, ductile, and shiny
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Alkali Metals Group 1 elements are known as Alkali Metals Alkali metals include Li, Na, K, Rb, Cs, Fr Alkali metals are generally dull, soft, and reactive – rarely found as free elements
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Alkaline Earth Metals Group 2 elements are known as Alkaline Earth Metals Alkaline earth metals include Be, Mg, Ca, Sr, Ba, and Ra Alkaline earth metals are harder, denser, and stronger than alkali metals Less reactive than alkali metals, but still rarely found as free elements
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Transition Metals Elements in groups 3-12 (3B-2B) are known as Transition Metals Transition metals include Mn, Fe, Ag, Au, Mo, etc. Lanthanide and Actinide Series elements fill in the f orbitals – known as inner transition elements
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Metalloids Elements that border the staircase on the periodic table are known as Metalloids Metalloids include: B, Si, Ge, As, Sb, Te, Po, At Metalloids have properties of both metals and nonmetals
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Nonmetals Nonmetals are found to the right of the staircase on the periodic table Nonmetals generally become anions What is an Anion? How are they formed? Negatively charged atom - Gain electrons Nonmetals are often gases or dull, brittle solids Nonmetals generally show poor conductivity, ductility, and malleability
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Halogens Group 17 elements are known as Halogens Halogens include F, Cl, Br, and I Halogens are the most reactive nonmetals – often found in compounds
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Noble Gases Elements in group 18 are known as Noble Gases Noble Gases include He, Ne, Ar, Kr, Xe, Rn Noble gases are extremely unreactive
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Legend
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Pure Substances Cannot be physically separated Every sample has the same characteristics and they can be used to identify a substance
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Elements Are made up of ONE type of atom Atoms are the smallest unit of an element that maintains the chemical identity of that element They can be found on the Periodic Table Examples: Carbon, Nitrogen, Calcium
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Compounds Can be broken down into simple stable substances Are made up of two or more types of atoms that are chemically bonded Examples: Water (H 2 O), sugar (C 12 H 22 O 11 )
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Mixtures A blend of two or more kinds of matter, each which retains its own identity and properties
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Homogeneous Mixtures Have uniform composition Also known as SOLUTIONS Examples: salt water, tea
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Solutions ALLOYS are solid solutions that contain at least 1 metal They are blended together so that they have more desirable properties Some alloys you may know are: Stainless Steel: iron, chromium, and zinc Brass: zinc and copper Bronze: tin and copper Sterling Silver: copper and silver
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Heterogeneous Mixtures Do not have uniform composition You can see the particles in them Examples: Sand on the beach (contains sand, shells, rocks, bugs, etc) Soil (contains dirt, rocks, worms, etc) Chicken Soup (contains water, chicken, veggies etc)
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Suspensions A heterogeneous mixture where the solid particles eventually settle out of solution Examples: Muddy water Mixtures of two solids Paint
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Properties of Matter All pure substances have characteristic properties Properties are used to distinguish between substances Properties are also used to separate substances
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Physical Properties A Physical Property is a characteristic that can be observed or measured without changing the composition of the substance Physical properties describe the substance itself Examples Physical State Color Mass, shape, length Magnetic properties
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Chemical Properties A Chemical Property indicates how a substance will react with another Chemical properties cannot be determined without changing the identity of the substance Examples: Iron Rusting Silver Tarnishing
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Physical Changes A Physical Change is a change in a substance that does not alter the substance’s identity Examples: Grinding Cutting Melting Boiling
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Chemical Changes A change in which one or more substances are converted into different substances is called a Chemical Change Signs of a Chemical Change: Color Change Gas is Released Temperature Change Precipitate – Solid falls out of solution Substance Disappears
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Electrons Electrons fill in an atom in energy levels Electrons occupy the LOWEST available energy level Energy Levels hold limited amounts of electrons 1 st Level – 2 electrons 2 nd Level – 8 electrons 3 rd Level – 18 electrons 4 th Level – 32 electrons
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Chlorine (Cl) P = 17 N = 18 E = 17
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Nitrogen (N) P = 7 N = 7 E = 7
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Aluminum (Al) P = 13 N = 14 E = 13
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Valence Electrons Electrons in outermost shell that determine chemical behavior Maximum of 8 valence electrons Atoms with same valence electrons will act similarly Group 1 elements? 1 valence electron Group 17 elements? 7 valence electrons
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How Atoms Combine Two or more atoms that are chemically combined make up a compound The combination results in a chemical bond, a force which holds elements together in a compound
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Covalent Bonds Covalent Bonds are formed when atoms in a compound share electrons Molecule – two or more atoms held together by a covalent bond Usually occurs between nonmetals
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Covalent Bonding in Water
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Ions An atom that has gained or lost an electron is called an ion. Multiple atoms can combine to form an ion – called a Polyatomic Ion Silicate (SiO 4 4- ) and Carbonate (CO 3 2- ) are important in forming materials at Earth’s Surface
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Ionic Bonding Positive and negative ions attract each other Ionic Bonds occur when oppositely charged ions form a compound Usually consist of 1 metal and 1 nonmetal Positive ion written first in chemical formula (NaCl) Ionic compounds have a neutral charge
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Ionic Bonding in NaCl
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Metallic Bonds Metals share valence electrons between all atoms Like a group of positive ions in a sea of electrons
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Acids and Bases An Acid is a substance that produces Hydrogen Ions in water (H + ) Acids: Sting to the touch Taste Sour React with metals
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Acids and Bases A Base is a substance that produces hydroxide ions (OH - ) in water Bases Are slippery to the touch Taste Bitter Do not react with metals
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pH Scale Measures the amount of hydrogen ions in a solution 0 - 6 Acidic 7 = Neutral 8 - 14 Basic
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Indicators Indicators are substances that turn colors at different pH levels Examples: Litmus Phenolphthalein Base indicator Universal Indicator: ACID NEUTRAL BASE Cabbage Juice ACID NEUTRAL BASE
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