Chemistry Flashcards
_______________
- The number of protons in the atoms nucleus
Atomic number
_______________
- The number of protons and neutrons in the atoms nucleus
Mass number
_______________
- Same number of protons and electrons, but different number of neutrons
Isotope
_______________
- An atom that has lost electrons
Cation
_______________
- an atom that has gained electrons
Anion
True or false : Bohrs model explains emission of specific spectral lines from hydrogen atom
True
_______________
- are accurate models of where electrons reside outside of nucleus
Orbitals
The s orbital has ______ orientation(s)
The p orbital has ______ orientation(s)
The d orbital has ______ orientation(s)
1
3
5
_________ principle
- atomic orbitals are filled from the lowest energy orbital to the highest energy orbital until all electrons are used
Aufbau principle
____________
- Electrons in the highest energy orbitals
Valence electrons
____________principle
- only 2 electrons may be placed in one or a little at a time and they must have opposite spins
Pauli exclusion principle
____________
- orbitals of equal energy must first be filled singly with electrons of the same spin and then paired with electrons of opposite spin
Hund’s rule
____________
- when an atom absorbs energy, its electrons move to higher energy levels
Energy transition
____________
- The energy level of an electron prior to energy absorption
Ground state
____________
- The energy level of an electron after energy absorption
Excited state
An electron stays at the excited state for a brief period, and then relaxes back to the ground state causing energy to be admitted as _______________
Electromagnetic radiation
____________ can be produced from both atomic energy, absorption and emission experiments (characteristic of the element, and can be used to determine the identity of an unknown substance)
Spectra
____________
- experimental procedure to determine precise mass and relative abundance of isotopes in a substance
Mass spectrometry
____________ operation
- a sample is introduced into the instrument and vaporized
- Vaporize the particles are ionized (creating positively charged radical cations)
- Ions undergo further fragmentation into lower mass ions (occurs through a magnetic field, which separates them by mass)
- Ions leave magnetic field and are detected in the order of highest to lowest mass
Mass spectrometer
____________
- Fragmentation patterns
- Are unique to the substance
- Provide molecular weight directly
- Molecular formula can be determined
Spectra
____________
- A property predictable from the elements position in the periodic table
Periodic property
Atom size (radii) __________ down a group & __________ from left to right across period
Increase
Decrease
Atomic radii __________ with gain of electrons & __________ with loss of electrons
Increase
Decrease
____________
- Energy required to remove an electron from an atom or ion and its gaseous state
- values always positive
Ionization energy
____________
- removal of highest energy electron
First ionization energy
Ionization energy generally __________ down a group & __________ from left to right
Decrease
Increase
_______________
- Energy change associated with gain of an electron by an atom in gaseous state
- usually exothermic
Electron affinity
Most groups do not exhibit a trend in electron affinity but group 1 elements become more positive down a group
Electron affinity generally becomes more __________ from left to right in a period
Negative (exothermic)
_______________
- The ability of an atom to attract electrons in a covalent bond
- Values range from 0.7 - 4.0 using the pauling scale (values are unitless)
Electronegativity
Electronegativity _________ down a group & __________ from left to right in a period
Decreases
Increases
_______________
- electrostatic attraction between 2 oppositely charged ions (usually a metallic cation & a nonmetallic anion)
- Due to lowering of potential energy between oppositely charged ions
Ionic bond
The potential energy of attraction between two oppositely charged ions is estimated by using _______________
Coulomb’s law
_______________
- are energy associated with formation of a crystal of alternating ions from gaseous ions (values are always negative)
Lattice energy
As ions become larger, the △H-lattice becomes less __________
Less negative (less exothermic)
As charges of ions increase, △H-lattice becomes more __________
Negative (more exothermic)
_______________
- when 2 atoms share valence electrons between their nuclei
- there potential energies are lowered through electrostatic attraction
- Typically nonmetals
Covalent bonds
_______________
- to the drawing, representing covalent bonds between atoms as shared or transferred electrons
- Based on the molecular formula
Lewis structures
All elements except for _____ & _____ prefer 8 electrons around their nuclei
H
He
When there are several Lewis structures, then ____________ occurs and they can be combined to form a hybrid
Resonance
_______________
- used to determine the best Lewis structure
- FC = Atoms Group # - (bonds + unpaired electrons)
- “normal valence - (lines +dots)”
- a compound’s total charge must equal the sum of all its atoms formal charges
Formal charge
When 2 atoms in a covalent bond have the same electronegativity then the atoms share valence electrons equally so such bonds do not have a dipole moment and are termed _______________
Nonpolar
When atoms in a bond have different electronegativities in a dipole moment, occurs in the covalent bond is termed _______________
Polar
When the difference in electronegativites between atoms in a bond is very large then an __________ interaction occurs because electrons are transferred to the more electronegative atom
Ionic
_______________ theory
- one of several techniques that can be used to predict the shapes of molecular compounds
- based on the idea that electrons with similar charges repel each other
- when only bonding electron pairs are considered than 5 shapes are predicted
- other shapes are predicted when a pair of bonding electrons is replaced with a pair of non-bonding electrons
Valence Shell Electron Pair Repulsion theory
VSEPR
When 1 bonding group of the principle tetrahedral shape is replaced with a lone pair. The shape is now called _______________ and has bond angles of _________
Trigonal pyramidal
~107 degrees
When 2 bonding groups of the principal tetrahedral shape is replaced with two lone pairs in the shape is called _______________ and had bond angles of _________
Bent
~105 degrees
True or false : Polarized bond exist in a molecule than the overall molecule may or may not be polar because the shape in the orientation of dipole moment can be used to predict Molecular polarity
True
_______________ theory
- approach to predicting length and strength of covalent bonds qualitatively and molecular compounds
- also predicts 3D shapes of molecules
3 basic principles
- Overlap of atomic orbitals containing unpaired valence electrons
- Localization of valence electrons in the orbital overlap region between atoms
- Formation of hybrid orbitals from atomic orbitals to optimize orbital overlap between bonding atoms
Valence bond theory
___________ bonds
- form by the end-to-end overlap of atomic and hybrid orbitals containing unpaired electrons
- bonded atoms share electrons between them
Sigma bonds
___________ bonds
- form by side to side, overlap of atomic orbitals, usually p orbitals
-are longer & only about 3/4 as strong as sigma bonds
- can form only in conjunction with sigma bonds (cannot exist without a sigma bond)
Pi bonds
_______________
- compounds differ in some ways, but have same molecular formula
Chemical isomers
_______________
- same molecular formula, but differ in the way the atoms in the molecule are bonded to each other
Structural isomers
“Constitutional isomers”
_______________
- same molecular formula and connectivity a differ in the way the atoms are arranged
- cannot be interconverted by sigma bond rotation (“single bond”)
Stereoisomers
_______________
- usually a carbon atom that is sp3 hybridized & has 4 different atoms or groups of atoms attached to it
Chirality Center
Stereoisomers have 2 categories
_______________
_______________
Enantiomers
Diastereomers
_______________
- nonsuperimposable mirror images of each other
- always come in pairs (the left and right handed isomers of a compound)
- always contain at least 1 chirality center
- a pure enantiomer is optically active & rotates plane-polarized light
Enantiomers
_______________
- not mirror image stereoisomers of each other
- includes all forms of stereoisomers except enantiomers
Diastereomers
Process of R and S assignment of absolute stereochemistry to chirality centers
- each of 4 groups bonded to chiral carbon in chirality center is assigned a priority
- priorities are assigned using the _____________________ protocol
- lowest priority group is position behind chiral carbon, leaving the remaining high priority groups in a trigonal planar configuration. If priorities of groups around the chiral carbon are 1 to 2 to 3 in a clockwise direction then the center is designated R & and if the priorities are counterclockwise in the center is designated S
Cahn-Ingold-Prelog (CIP) protocol
Stereoisomers of certain organic compounds (specifically alkenes) occur as a type of diastereomer & can be distinguished as ________ or ________
Cis-
Trans-
__________ configuration
- 2 atoms of the same type are on opposite sides of double bond
Trans- configuration
___________ configuration
- 2 atoms of the same type are on the same side as of double bond
Cis- configuration
_______& ________ assignment
- common protocol to distinguish alkene stereoisomers
E (entgegen = opposite)
Z (zusammen = together)
E and Z designations are most commonly used when there are no like groups attached to the double bond, but they can be used to indicate the stereochemistry of any alkene. The procedure for assigning E and Z to a specific stereoisomer (use C-I-P prioritization rules)
- When highest priority groups are on opposite sides of the double bond, the isomer is designated as _____
- when highest priority groups are on the same side of the double bond, it is designated as _____
E
Z
_______________
- heat required to raise the temperature of a substance by 1°C
Heat capacity
_______________
- heat required to raise the temperature of 1 g of a substance by 1°C
Specific heat capacity
_______________
- temporary structural isomerism to study energy changes because sigma bonds have freedom of rotation (parts of molecule can move many ways)
Conformational analysis
_______________
- 2 different conformational if structures of ethane
Sawhorse structures
____________ conformations of ethane
- all H aligned & high energy due to torsional strain
____________ conformations of ethane
- no H aligned & low energy
Eclipsed conformations
Staggered conformations
A ___________________ , useful in alkane stereochemistry, visualizes the conformation of a chemical bond from front to back, with a line representing the front atom and a circle representing the back carbon. The carbon atom at the front is called proximal, while the atom at the back is called distal.
Newman projection
In cyclohexane conformations the lowest energy conformation is called the _________ (with almost no ring strain)
Chair
Chair conformation has 2 different types of substitute bonding positions where H & other substitutes are attached to ring. These positions are ________ (bonds, extend directly above & below the ring) and ____________ (bonds are oriented at ~ 45° angles around the equator of the ring)
Axial
Equatorial
Any chair conformation with a substitute larger than an H-atom has lower energy (more stable) with substitute in equatorial position, so lowers ____________
Steric strain
True or false:
Gases differ from the condensed phases of liquids & solids in a number of ways
- Gas volume changes greatly with pressure
- Gas volume changes greatly with temperature
- Gases have low viscosity
- Gases are always miscible with each other
True
True or false:
Ideal gases do not exist. A true ideal gas would be made up of molecules that have no interaction with each other (no attractive forces) and zero volume. Helium is the closest to an ideal gas.
True
Measurable parameters of ideal gases can be estimated from
_____________ law
_____________ law
_____________ law
Charles law
Boyles law
Avogadro’s law
_______________
- volume of gas directly proportional to temperature
- P and n held constant
Charles law
_______________
- volume of gas inversely proportional to pressure
- T and n held constant
Boyles law
_______________
- volume of gas is directly proportional to amount of gas
- P and T held constant
Avogadro’s law
____________ law
- PV = nRT
- Basic gas relationships can be combined to give a single law (Charles, Boyles, & Avogadro’s)
Ideal gas law
_______________
- models, an ideal gas as a collection of point particles constantly in motion & undergoing completely elastic collisions
- Explains Avogadro’s law
- For any ideal gas at standard temperature and pressure (STP) [1 mole gas = 22.4 L]
Kinetic-molecular theory
_______________
- any gas mixture, each gas ask independently so that any overall property of the mixture is the sum of the properties of the individual components
- Some of the individual gas pressures (partial pressures) must equal total pressure (P-total = P-a + P-b + P-c …..)
- if total pressure of mixture is known, partial pressure of any component can be determined
Dalton’s law of partial pressures
_____ gas behavior
- Real gases deviate from ideal gas properties to different degrees under various conditions
- At high pressures (>20 atm) the molar volume is greater than that of ideal gas
- At low temperatures (<200K), the stronger attractions between gas particles lower number of collisions on surface of a container, lowering pressure compared to ideal gas
Real
The _____________ equation is used to correct for high pressure & low temperature effects
- P + a(n/V)^2 • (V - nb) = nRT
- P + a(n/V)^2 : corrects for intermolecular forces
- (V - nb) : correct for molar volume (a & b are constants for specific gases)
Van der Waal’s equation
__________
- A condensed phase of matter
- atoms & molecules packed as closely as in a solid, but can move relative to each other
- A fixed volume but not a fixed shape (shape of its container)
- Properties : vapor pressure, boiling point, viscosity, & surface tension
Liquids
__________
- attractive & repulsive forces between atoms and molecules in a liquid
- Hold condensed phases of matter together
- Ion-dipole, H bonds, dipole-dipole, & London dispersion
Intermolecular forces
__________
- between ion and oppositely charged end of polar molecule
Ion dipole
