Precision How close your answers/measurements are to each other Dependent Variable -The variable you are measuring -on the y-axis of a graph -what comes after then in your if/then statements Element -A substance made of only one type of atom -found on the periodic table ex: Titanium (Ti) Heterogeneous Mixture A substance whose properties differ throughout ex: salad Physical Change A change in a material that does not change its composition, for example, a change in size or shape Extensive Property A property of a material that depends on the amount of substance present ex: mass Solid particles are tightly packed and vibrating in one spot resulting in definite volume and shape. Accuracy How close your answers/measurements are to the correct answer/measurement Constants variables that are kept the same in an experiment to ensure its validity Compound -A substance made of 2+ atoms chemically combined -always has a formula ex: sugar (C6H12O6) Colloid A substance that appears homogeneous but has small particles of one material suspended in another ex: fog, smoke, milk Chemical Change A change in a material that changes its composition evidence: light produced, gas (bubbles) produced, precipitate formation, color change, temperature change, or odor Physical Property A property of a substance that can be observed without changing its composition ex: color, melting point Liquid particles are loosely packed. They are mobile but still attracted to each other which results in definite volume but indefinite shape. Independent Variable -The variable you are manipulating in the experiment -on the x-axis of a graph -what comes after if in your if/then statement Control Group -a set of things not experimented on for the sake of comparison -the normal group in an experiment Solution -homogeneous mixture -one substance dissolved in another ex: kool-aid Suspension A substance that appears homogeneous but has large particles of one material suspended in another that eventually separate due to gravity ex: Mustard Intensive Property A property of a material that depends only on the composition, not the amount ex: temperature Chemical Property A property of a substance that, when observed, changes the composition of the material ex: flammability Gas particles are in rapid random motion. The particles are no longer attracted to each other which results in indefinite volume and shape. Physical Separation Separation of pieces of a heterogeneous mixture through the use of fingers or forceps. Ex: pepperoni off of a pizza Filtration Separation of a non-dissolved solid from a liquid using a filter or colander to distinguish by size. Ex: coffee grounds vs water Evaporation Separation of a dissolved solid from a liquid by the leaving the container open to air ex: saltwater into salt + water
Magnetism Separation of materials made of Fe, Ni, or Co through the use of a magnet ex: paperclips vs rubber bands Plum Pudding Model The atom consists of negative particles (discovered through the cathode ray experiment) suspended in a sea of positive charge. By: JJ Thompson Quantum Mechanical Model charged nucleus with the electrons in different shaped pockets of space (because electrons move at the speed of light and are therefore difficult to pinpoint) at varying energy levels. By: Schrodinger Electron Negatively charged particle found outside the nucleus of the atom **changes in the number of electrons results in an ion Atomic Mass The weighted average mass of the isotopes of an element, a number with a decimal, reported on the periodic table Half-Life The amount of time it takes half of a sample of radioactive (unstable) parent isotope to decay to stable daughter isotopes Distillation Separation of a mixture of liquids by their boiling point ex: moonshine Planetary Model charged nucleus (discovered through the Gold Foil Experiment) with rings of electrons outside the nucleus By: Ernest Rutherford Proton Positively charged particle found in the nucleus of the atom **The number of protons defines what element the atom is Isotope A version of an element with a different mass Fission The process by which 1 large nucleus splits into 2+ smaller nuclei sometimes as a result of being bombarded with neutrons. -used in nuclear power plants and U-bombs, releases a LOT of energy -produces toxic/radioactive waste Energy Level A period of the periodic table (row), a ring of the Bohr model, or a set of clouds (ex: 2s and 2p) in the quantum mechanical model Dalton/Conservation of Matter The atom is a solid sphere that cannot be created or destroyed, only rearranged into whole number ratios in the formation of compounds Bohr Model charged nucleus with the electrons outside, in set energy levels (discovered with the flame test) By: Neils Bohr Neutron Neutrally charged particle found in the nucleus of the atom **changes in the number of neutrons results in an isotope Mass Number The mass of the isotope being considered, a whole number, reflecting the number of protons + the number of neutrons ex: Carbon-14 has a mass of 14 which means it has 6p + and 8 n 0 Fusion The process by which 2+ small nuclei combine to form 1 larger nuclei, typically under high temperature and pressure. -occurs in the center of the sun -produces even MORE energy than fission -has safe products Hund's Rule orbital diagram, place one electron in each orbital (blank) before pairing.
Pauli Exclusion Principle orbital diagram, place one arrow up and one arrow down (electrons of opposite spins) in each orbital (blank) Frequency How many waves pass a given point per second -The lower the wavelength, the higher the frequency -Higher frequency waves have more energy Lewis Dot Diagram A depiction of an element's symbol, with the number of valence electrons around it. -place one electron in each direction (North, East, South, West) before pairing. Group Read top to bottom on the periodic table There are 18 of them that are also called families Transition Metals Elements in the 3 rd -12th columns of the periodic table (short columns) whose charge/number of valence electrons can vary Noble Gases Elements in the 18 th column, or 8 th tall column of the periodic table that have a full valence shell and therefore resist bonding Aufbau Principle orbital diagram, follow the downward diagonal diagram instead of reading left to right ex: 3s3p4s3d NOT 3s3p3d4s Speed of Light 3 x 10 8 m/s Octet Rule Atoms will gain or lose electrons in a chemical bond to have a full valence shell of 8 electrons Alkali Metals Elements in the first column of the periodic table with one valence electron Rare Earth Metals Elements in the bottom section (f-block) of the periodic table whose charge can vary Metals Elements that are shiny, conduct heat /electricity well, and react with acid. These make up about 80% of elements and are found in columns 1-12 and underneath the staircase on the right hand side of the periodic table. Wavelength The length of a wave, measured in meters, from one peak to the next. Low wavelength light is near the violet side (UV, X-ray, gamma) and high wavelength light is near the red side (infrared, microwave, TV). Valence electron An electron in the outermost ring of the Bohr model, used in bonding Period Read left to right on the periodic table There are 7 of them that represent the seven possible energy levels in the Bohr model. Alkaline Earth Metals Elements in the second column of the periodic table with two valence electrons Halogens Elements in the 17 th column, or 7 th tall column, of the periodic table with seven valence electrons Metalloids Elements found along the staircase on the periodic table that can have properties of both metals and nonmetals
Atomic Radius (and trend) -The size of the atom -increases moving down the periodic table because there are more rings of electrons -decreases moving across the because there are more protons being added to the nucleus that pull in the same number of rings of electrons Cation A positively charged ion formed through the loss of electrons, typically by metals Ionic Bond A transfer of electrons from a metal to a nonmetal Properties of a Metallic Bond -malleable -ductile -conducts heat/electricity well Steric Number The number of things (lone pairs + connected atoms) on the central atom of a covalent compound Nonpolar Bond When the electronegativity difference between two nonmetals is less than 0.5 -electrons are shared evenly VSEPR Theory -Valence Shell Electron Pair Repulsion -lone pairs and bonded atoms around the central atom of a covalent bond will rearrange themselves in 3D space to get as far apart as possible Electronegativity (and trend) -an atom's desire for electrons/ how well the nucleus works to pull in more electrons -decreases moving down the periodic table because the increased number of rings in the Bohr model shields the power of the nucleus -increases moving across the (except column 18) because the valence shell is closer to being full Anion A negatively charged ion formed through the gain of electrons, typically by nonmetals Properties of an Ionic Compound -crystal structure -conducts electricity when melted or dissolved only -high melting point Covalent Bond When electrons are shared between two nonmetals Lone Pair A pair of non-bonded electrons on the central atom of a covalent compound Polar Compound When one side of the compound (around the central atom) looks different from the other Intermolecular Forces The forces that hold one covalent compound to another that in order of strength are Hydrogen attraction, Dipole, and London Dispersion Force Ionization Energy -The energy it takes to steal an electron from the valence shell of an element -decreases moving down the periodic table because the increased number of rings in the Bohr model shields the power of the nucleus -increases moving across the because there are more protons being added to the nucleus that pull on the electrons Polyatomic Ion 2+ atoms chemically combined that have a charge ex: Sulfate SO4-2 Metallic Bond -also called an alloy -consists of metal cations in a sea of electrons ex: cast iron, stainless steel Single vs Double vs Triple Bond When 2 electrons, 4 electrons, or 6 electrons total are shared respectively between two nonmetals Polar Bond -When the electronegativity difference between two nonmetals is 0.5-1.9 -electrons are shared unevenly Nonpolar Compound When all sides of the compound (around the central atom) look the same Hydrogen Attraction When the H of one molecule is attracted to a highly electronegative element (genuine element- H, O, N, F, Cl, Br, or I) on another molecule
Dipole When the positive side of a polar molecule is attracted to the negative side of another polar molecule Acid A compound whose formula starts with hydrogen Mole A unit of material meaning 6.02 x 1023 particles/molecules/formula units/atoms Molecular Formula The true formula for a compound found by dividing the given mass in a problem by the mass of the empirical formula then using this number as a multiplier of the empirical formula's subscripts London Dispersion Force A weak attraction between nonpolar molecules due to the random movement of electrons occasionally resulting in one side of the molecule being more negative than the other Greek Prefixes 1-Mono 2-Di 3-Tri 4-Tetra 5-Penta 6-Hexa 7-Hepta 8-Octa 9-Nona 10-Deca Formula Mass (Molar Mass) The mass of a compound found by adding the masses of all the elements together The number of liters 1 mole of gas occupies at STP 22.4 Diatomic Element An element that, when left alone, pairs with itself -genuine elements: H, O, N, F, Cl, Br, I ex: H2, O2, N2, etc Roman Numerals for Transition Metal Charges I- one II- two III- three IV- four V- five VI- six Empirical Formula The basic formula for a compound found by using the percent compositions given and following the rhyme: percent to mass, mass to mole, divide by small, multiply 'til whole Equation for Density *broken heart density= mass/volume Equations/Constants Density= mass/volume Mass Number= protons + neutrons 6.02* 10 23 things= 1 mole 22.4 L of gas= 1 mole (at STP) Weighted Average= % isotope 1*mass isotope 1 + % isotope 2* mass isotope 2 Percent composition= (mass of all atoms of an element in a compound/mass of compound) *100 C= λ*ν (c= 3.0x10 8 m/s) E= h*ν (h= 6.63*10-34 Js)