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Midterm Review ( CHEMISTRY )
Terms in this set (74)
Use the markings and provide one estimated digit at the end.
1. All nonzero digits are significant.
2. All digits placed between nonzeroes are significant.
3. All leading zeroes are not significant.
4. All trailing zeroes are significant after the decimal point.
5. Trailing zeroes to the left of a decimal point are only significant when the decimal point is visible.
6. In scientific notation, it will always show the appropriate number of significant figures.
7. The given in a DA problem will always have the number of SF that should be in the final answer.
1. Adding and subtracting should have a rounded answer to the same number of decimal places as the number with the least number of decimal places.
2. Multiplying and dividing should have a rounded answer to the same number of SF as the number with the least SF.
The fixed ratio of an object's mass to its volume. It is an intrinsic property and is unique to each pure substance. If something is less dense, it will float in water (1.00 g/mL), while if it is more dense, it will sink.
Equation: d = m / v
Simplest piece of matter; found on periodic table. It is ONE type of atom.
Combinations of different types of elements in a fixed ratio; atoms are fixed by chemical bonds.
Made up of pure substances, no chemical bonds are formed. It can be separated by physical means.
A mixture that appears consistent in composition; no clear separations of material.
A mixture with clear separations (visually); not consistent throughout. They would have different shapes, different densities, different materials visible.
Smallest particles, homogeneous, transparent, completely allows light to pass through
Homogeneous, exhibits the Tyndall effect. Particles will not settle out. (i.e. jello, fog, milk)
Heterogeneous, particles can be filtered or settle out. (i.e.: muddy water)
Light passes through in the form of a beam due to light colliding with larger-sized particles.
Observed/measured without changing the sbustance's composition
(i.e.: color, state of matter, boiling point, magnetism, conductivity)
Consists of the ability of a substance's composition to change, cannot be tested by looking and identifying.
(i.e.: ability to rust (oxidation), corrosion (acid), flammability, reacts with water, inert (resists change), toxicity, heat/combustion
Not dependent on size, they rely on nature.
(i.e.: density, melting point, boiling point)
Based on a sample size, depends on the amount of a substance.
(i.e.: mass, volume)
In which a substance undergoes a change that does not alter composition. It can be reversible or irreversible.
(i.e.: changes of state, dissolving, cutting, reshaping, etc.)
In which a a substance undergoes a change that chemically alters the composition. It is irreversible and new substances are formed. Synonymous with chemical reaction.
(i.e.: burning, cooking, fermenting, decomposing, disintegration, corrosion, etc.)
Signs of Chemical Change
1. Change in temperature *
2. Change in color *
3. Formation of gas / effervescence (bubbling, fizzing, etc)
4. Production of light (spark, for instance)
5. Production of a precipitate (two liquids/solutions form a solid)
* - Not a sign of chemical reaction
Chemical Equations/Reactions Set Up
Reactants --> products
Reactant 1 + Reactant 2 --> Product 1 + Product 2
HCl + NaOH --> H₂O + NaCl
Law of Conservation
All chemical changes are governed by scientific law. Mass/matter/energy cannot be created/destroyed in a normal chemical reaction, it transforms from one form to another. Specifically, in an isolated system, the mass/matter/energy should remain constant.
Discovered the electron by experimenting with Cathode Ray Tubes and diverting the cathode ray with a magnet. He observed: the negative pole of the magnet near the ray led to the ray deflecting away, the positive pole attracted the magnetic field, and the cathode ray was travelling from cathode (-) to anode (+). This led to the discovery of the electron.
"Plum Pudding Model." Looks like a chocolate chip cookie, with negative particles (electrons, in circles) and positives floating around (no circles).
Discovers the atomic nucleus after doing the gold-foil experiment (where positive/alpha particles were fired at a piece of gold foil).
1. a large majority of alpha particles passed directly through the foil.
2. some particles were greatly reflected.
3. rarely, a particle would bounce back towards the source.
1. most of an atom consists of empty space
2. there is a condensed, positive mass in an atom called the nucleus.
Contains a positive nucleus in the center and negative particles floating around it.
Modern Atomic Model
Electron cloud model; nucleus at the center and the darkest color around the nucleus as it fades out going further than the nucleus. The darkest color indicates the most likely probability of electrons being there. Discovered by Erwin Schrodinger.
Quantum Mechanics - Principal Quantum #
Energy Level, otherwise known as n [n=1, 2, 3, 4, 5, 6]. There is no n=0, because that is the nucleus and electrons do not exist in the nucleus.
Quantum Mechanics - Secondary Quantum #
Sub-Level, describes the shape of the sublevel and is defined by l.
~ l=0 -- s sublevel (spherical)
~ l=1 -- p sublevel (dumbell shaped)
~ l=2 -- d sublevel (clover shaped)
~ l=3 -- f sublevel (complex shape)
Range: l=0 .... (n-1)
-- Range from 0 to the energy level number minus 1.
Quantum Mechanics - Magnetic Quantum #
Divides sublevels into individual orbitals, defined by m(l).
Range: m(l)=-l ... +l
-- Negative l to positive l.
Quantum Mechanics - Spin Quantum #
How an electron spins while making revolutions on the orbitals. Can only be +1/2 or -1/2. Defined by m(s).
Not a permanent # due to spin flips.
Each orbital in each energy level can hold a maximum of 2 electrons ALWAYS, but will differ in sublevels.
> s sublevel - 1 orbital, 2 electrons.
> p sublevel - 3 orbitals, 6 electrons
> d sublevel - 5 orbitals, 10 electrons
> f sublevel - 7 orbitals, 14 electrons
energy levels & sublevels:
> n=1 contains s-sublevel (l=0) -- 2 total electrons
> n=2 contains s + p sublevels (l=0,1) -- 8 total electrons
> n=3 contains s, p, + d sublevels (l=0,1,2) -- 18 total electrons
> n=4 contains s, p, d, and f sublevels (l=0,1,2,3) -- 32 total electrons
Electrons Filling Orbitals - Rules
1. Aufbau Principle
Electrons will fill available atomic orbitals of lowest energy first (electrons are lazy).
2. Pauli Exclusion Principle
Each atomic orbital can, at most, hold 2 electrons. One electron will spin +1/2, and the other, -1/2.
3. Hund's Rule
When electrons are filling orbitals, each orbital will receive 1 electron before any orbital receives two (the second electron will be -1/2 if the first is +1/2 spin, vice versa). The electrons will fill all orbitals in one sublevel before moving onto the next one.
Mapping technique for electrons. Each neutral, stable atom has a unique electron configuration.
Full Electron Config.:
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f14, 5d10, 6p6, 7s2, 5f14, 6d10, 7p6
Noble Gas / Abbreviated Configuration
Using noble gases as a reference atom since they have a full outermost sublevel (end in p⁶), you show the noble gas symbol in brackets and then follow the brackets with appropriate electron configuration.
Silver: [Kr] 5s2, 4d9
Krypton: [Ar] 4s2, 3d10, 4p6
Uranium: [Rn] 7s2, 5f3
Configuration of Ions
Write the regular electron configuration for the element as if it were neutral. Then, take away or add as many electrons that were gained/lost when the element became an ion.
Cl: 1s2, 2s2, 2p6, 3s2, 3p5
Cl(1-): 1s2, 2s2, 2p6, 3s2, 3p6
Measured in joules, achieved by multiplying Plank's Constant and the Frequency
Crest to crest or trough to trough, the length measured between. (typically measured in nm or m)
How many times waves would pass a certain point in a certain amount of time. Represented by v. (typically measured in Hz or s^-1)
Wavelength and frequency have an inverse relationship.
Frequency and energy have a direct relationship.
Wavelength and energy also have an inverse relationship.
Theory of Light Emission
When electrons are excited to a higher energy level, the electrons want to return back to the degenerate energy level. It releases energy in the form of light to fall back down.
Theory of Color
When white light falls onto objects, the object absorbs all colors except the color that it is perceived as. When light falls on this object, the electrons will be excited to a higher energy level. In order to fall back to a lower energy level, the electrons release energy in the form of light, or photons. The color of the photons is the color that the object does not absorb. The photons are reflected off the object and its wavelengths travel to our eyes, which transmits the color of the object via the brain.
Each element has a unique atomic spectra.
Continuous Spectrum: All visible wave lengths, white light.
Emission Spectrum: Each element releases photons of unique frequency that builds an analytical spectrum of frequency/wavelength that appear in lines; the element's fingerprint.
Absorption Spectrum: The opposite of emission; shows the excitation of electrons; scientists use emission/absorption to analyze stars
A form of an atom of an element that has the same number of protons but different numbers of neutrons.
Average Atomic Mass
Multiply the mass of each isotope by its natural abundance (decimal form) and then add the products.
M# = isotope mass
A#= relative abundance (% divided by 100)
(M#1 A#1) + (M#2 A#2) = Avg. Atomic Mass
Nuclear Symbol Notation
Mass number over top, atomic number on the bottom, to the left of the element symbol. [Ex: (197/79)Au.]
(Ex.: carbon-12, oxygen-16, selenium-76)
Subatomic particle with 1 amu and +1 electric charge.
Subatomic particle with 1 amu and 0 electric charge.
Subatomic particle with 0 amu and -1 electric charge.
The number of protons in an atomic nucleus of an element. It is also the number of electrons if the atom is electrically neutral. Each element has a unique atomic number.
The total number of protons and neutrons in an atom. Mass numbers are specific to every atom. The mass on the periodic table is the weighted average of the isotope in that element. You can subtract the number of protons to get the number of neutrons.
Otherwise known as a family, it is the term for a vertical column in the periodic table. Elements in the same group will have similar chemical and physical properties.
A horizontal row of the periodic table. The number of elements per period vary (as it is based on the orbital occupancy of an energy level). Although properties of elements will change as you move across a period, the pattern will repeat on the next period.
1A - Alkali Metals
2A - Alkaline Earth Metals
B (d and f blocks) - Transition Metals, Inner Transition metals
7A - Halogens
8A - Noble Gases
Trends - Electronegativity
The ability of an element/type of atom to attract electrons when in a compound.
Trend: Increases from bottom to top and increases left to right (for representative elements). This has a similar trend to ionization energy as they are opposites of each other. As electronegativity increases, more energy is required to eject the electron because the electrons are more attracted.
It does not affect noble gases as they do not form many compounds. Noble gases have an en=0.
Trends - Ionization Energy
The energy to eject an electron.
Trend: Increases from bottom top and increases from left to right. In a period, if the atomic radius is smaller, it requires more to remove an electron as the electron has a stronger charge to the nucleus (due to shielding). In a group, if the atomic radius is larger, the electron has less attraction to the nucleus and can be easily ejected.
Trends - Atomic Radius
Defined as half the distance between the nuclei of two atoms of the same element when joined.
Trend: Increases from top to bottom (due to shielding, aka adding more energy levels after each period, increases radius) and decreases from left to right (due to charge attractions; more electrons/protons = stronger attraction which pulls the atom closer together and decreases radius).
The electrons in the outermost energy level of an atom.
How Ions Form Based on Valence
Elements form ions based on their valence electrons and how easy it is to lose/gain. If an element has less than 4 valence electrons, it will lose those electrons and become a cation. If an element has more than 4 valence electrons, it will gain electrons and become an anion. If an element has 4 valence electrons, it can become a cation or an anion, depending on what it needs to be.
Excluding transition metals, the groups of the periodic table, from left to right, follow this for ionic charge:
1+, 2+, 3+, 4+/-, 3-, 2-, 1- 0.
An ion with a positive charge when it loses an electron.
An ion with a negative charge when it gains an electron.
Contained in the s and p blocks of the periodic table, they have predictable qualities.
Contained in the d and f blocks of the periodic table, they are more unpredictable and include the transition and inner transition metals.
A chemistry unit used to describe an amount of particles.
1 mol = 6.02 * 10²³ representative particles
Atoms - element (1 mol S = 6.02 * 10²³ atoms S)
Molecules - compound with nonmetals only (1 mol H₂O = 6.02 * 10²³ molecules H₂O)
Formula Units - compound with a nonmetal and metal (1 mol NaCl = 6.02 * 10²³ f.u. NaCl)
Atoms in Compounds
Since atoms are not the rep. parts for compounds , you must add the subscripts (if there are no subscripts near an element, add 1; if the subscript is after parentheses, distribute it).
CaCl₂ = 3 atoms -> 1 formula unit CaCl₂ = 3 atoms
The mass of exactly 1 mol in a substance. The molar mass of elements are the average atomic masses with the unit g/mol.
(# of Element
Average Atomic Mass) + (# of Element
Average Atomic Mass) + .... = Molar Mass
1 mol C = 12.01 g C
1 mol NaCl = 58.44 g NaCl
Elements that exist as 2 bonded atoms when not in a compound (isolated). Apply the unit molecules.
Hydrogen (H₂) = 2.02 g
Oxygen (O₂) = 32.00 g
Nitrogen (N₂) = 28.02 g
Chlorine (Cl₂) = 70.90 g
Fluorine (F₂) = 38.00 g
Bromine (Br₂) = 159.8 g
Iodine (I₂) = 253.80 g
1 mol = 22.4 L (Gas Only, @STP, 0 Celsius, and 1 atm)
In order to convert non-gases to liters, you must be given the density.
The correctness of something. (i.e. throwing darts and landing it in the center of a bullseye).
The closeness of two or more things. (i.e. if you repeatedly throw darts and they land in the same area).
Manipulated by user
Change caused by manipulating independent variable
Held constant during experimentation
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