Quarterly Study Guide - Chemistry PDF

Matter - Pure substances: contain only one type of matter. Can be elements or compounds - Mixtures: Contain one or more elements or compounds. Is not all one type - Compound: The combination of two or more types of atoms bonded together. The atoms in a compound can be separated chemicall...

Matter - Pure substances: contain only one type of matter. Can be elements or compounds - Mixtures: Contain one or more elements or compounds. Is not all one type - Compound: The combination of two or more types of atoms bonded together. The atoms in a compound can be separated chemically. - Element: The smallest unit of matter. All atoms are of the same type. Atoms of an element cannot be broken down, physically or chemically Periodic Table - The periodic table is arranged in order of increasing atomic number. The thing that differentiates one element from another is the number of protons in the nucleus - The periodic table contains three different types of elements: metals, nonmetals and metalloids - Metals generally lose valence electrons, become cations, are malleable, are ductile, have luster, conduct heat, and conduct electricity - Nonmetals generally gain valence electrons, are not malleable, are brittle, do not conduct heat or electricity - The seven metalloids are B, Si, Ge, As. Sb, Te, At - The periodic table is split up into groups (columns) and periods (rows). Elements in the same group have the same number of valence electrons and similar properties - The group 1 elements are alkali metals, have one valence electron, are highly reactive, conduct heat and electricity very well - The group 2 elements are the alkaline earth metals, have two valence electrons are highly reactive, conduct heat and electricity very well - The transition metals are in the middle of the periodic table, are ductile and malleable, have high melting point, form ions with multiple charges (oxidation states) form colored ionic compounds when dissolved in water - The group 17 elements are the Halogens, they are not very soluble in water, have seven valence electrons, have low melting and boiling points - The group 18 elements are the noble gasses. They have 8 valence electrons, are very unreactive, and exist mostly as gasses. - As you move left to right on the periodic table: - Atomic radius (size) decreases - Electronegativity (how strongly an atom attracts valence electrons) increases - ionization energy (how much energy is required to remove one valence electron) increases - As you move bottom to top on the periodic table: - Atomic radius decreases - Electronegativity increases - Ionization energy increases  - Metals on the left side of the periodic table (one or two valence electrons) are more reactive than other metals. - Nonmetals on the right side of the periodic table (six or seven valence electrons) are more reactive than other nonmetals. This excludes the noble gasses. Atomic Structure and Location - Protons and neutrons are found in the nucleus, electrons are outside the nucleus - protons = atomic number - protons + neutrons = atomic mass - atomic mass - atomic number = neutrons - neutral atoms have the same number of protons and electrons - The nucleus of an atom is small and dense and positively charged. Electrons are found outside the nucleus. - Rutherford did an experiment where he shot positive particles at gold foil. What he saw is that some of the particles went straight through while some were deflected wildly. This led to the conclusion that atoms are mostly empty space - Electrons can be found at different distances from the nucleus. These are referred to as energy levels. - The first energy level can hold 2 electrons, the second energy level can hold 8 electrons, the third energy level can hold 18 electrons - Inside of energy levels are space that electrons can be found, these are orbitals - The energy of electrons increases as they get farther from the nucleus (electrons in the third energy level are higher energy than electrons in the first energy level) - Electrons can move from between energy levels. - When electrons move from a lower energy level to a higher energy level they enter an excited state. This is called moving from the ground state to the excited state. - Electrons absorb energy to move to a higher energy level, and emit energy (as photons/light) when they return to the lower energy level (ground state) Calculations - All non zero numbers are significant - All zeroes between two numbers are significant - Zeroes to the right of a decimal point but before a number are not significant - Zeroes at the end of a number that contains a decimal point are significant - Exact numbers (like conversion factors) have an infinite number of significant digits - When multiplying/dividing using sig figs, the answer can only be as precise as  the least precise number in the problem (least precise number has least sig figs) - Steps: - Look at all numbers involved and determine which number has the least amount of significant figures and how many that is - Calculate - Round final answer so it has the correct amount of sig figs (same amount as the number in the calculation with the least sig figs) - When adding/subtracting using sig figs, the answer can only be as precise as the least precise place value in your calculation (more decimals = more precise) - Steps: - Look at all numbers involved and determine where the least precise place value is (Least precise place value is the last significant figure) - Calculate - Round final answer to the least precise place value - Density: D=m/v. The units of density are g/mL or g/cm3 (these two units are the same) - Percent error is the difference between the measured value and the actual value. % error = (measured - actual)/actual x 100 - The mass on the periodic table is the average atomic mass of all isotopes of an element - (isotopes are different versions of an element, same number of protons, different number of neutrons). - Average atomic mass is calculated by multiplying the mass of the isotope by the percent abundance (in decimal or percent form) Ionic Size - Adding electrons to an atom increases its size. Removing electrons reduces its size. - If you are comparing ions/atom with the same amount of valence electrons, the one that has the most protons in the nucleus will be the smallest - Adding or removing electrons changes the charge, or the oxidation state - Pattern in nature is that atoms will gain or lose electrons in order to have 8 valence electrons. - Hydrogen and Helium are the exception, both only have one energy level so can only have a max of 2 valence electrons. - If atoms are close to 8 valence electrons they will strongly attract other electrons (electronegativity) and do not want to lose valence electrons (ionization energy) - If atoms are not close 8 valence electrons they will not strongly attract other electrons and will be more likely to lose valence electrons (low IE) - Cations: positive, lose electrons - Anions: negative, gain electrons Lewis Dot Structures - Lewis Dots show the number of valence electrons that an atom has - Atoms in the same group will have the same lewis structure because they have the same number of valence electrons - Lewis Structures for anions show 8 lewis dots (full valence shell) to show it gained electrons - Lewis structure for cations show no lewis dots to show it lost electrons (next lowest energy level is full) Ionic Bonding - Ionic bonding occurs between a metal and a nonmetal. The nonmetal gains electrons to form an anion and the metal loses electrons to form a cation. - Attraction between the positive and negative ions hold them together (the ionic bond) - One type of metal combines with one type of nonmetal, but can have more than one ion of the metal or nonmetal - Metals lose e- (+ charge), nonmetals gain e- (- charge) - The overall charge of the combined ions must be zero - Include subscript to indicate if there is more than one atom of the metal or nonmetal - When writing the compound the metal is written first and the nonmetal second - When naming ionic compounds the metal is always written first. The name does not change - The nonmetal is always written second and the ending is changed to “ide” Criss Cross Method for Writing Ionic Compound Formulas - The charges of the ion become the subscript of the opposite ion (Charge of cation is the subscript of anion, Charge of anion is the subscript of cation) - Method steps: - Write charges of each ion - Criss cross charge to subscript of opposite ion - Get rid of charges - Simplify ratio Transition Metal Ionic Compounds - Because they have multiple possible forms, transition metals can form a variety of ionic compounds when combined with anions, depending on the charge - Writing the name:  - Cation is always written first. The name does not change - If it is a transition metal the name must be followed by the charge of the cation in roman numerals - *may also see this with lead (Pb) and tin (Sn) even though they are not transition metals - Name of the anion is written second, ending is “ide” - ex: Copper (I) Oxide Copper (II) Oxide - Writing the formula - Cation is written first and anion is written second, subscripts used to indicate how many of each ion - If it contains a transition metal you can use the opposite of the crisscross method to determine which ion is present. - The charge of ions must always add to zero. Polyatomic Ions and Ionic Compounds - Ionic compound is the attraction between positively charged cation and negatively charged anion - The cation or anion may be made of covalently bonded nonmetals - The lost or gained electrons are spread evenly among the covalently bonded ion - Ionic bonding with polyatomic contain both covalent and ionic bonding - Polyatomics: use the name directly from Table E in reference packet - Formula is always cation than anion, use subscripts to indicate if there is more than one ion - If there are multiple polyatomic ions, put parentheses around them and put the subscript outside the parentheses