General Chemistry Flashcards
Which subatomic particle is the most important for determining each of the following properties of an atom? charge, atomic number, isotope
Charge = electrons
atomic number = protons
isotope = neutrons
Determine the number of protons, neutrons, and electrons in each of these species? 18O, 18F
18O: 8 protons, 10 neutrons, 8 electrons
18F: 9 protons, 9 neutrons, 9 electrons
What are the definitions of atomic mass and atomic weight?
atomic mass: protons plus neutrons
atomic weight: the weighted average of the naturally occurring isotopes of an element
isotopes = same proton diff neutron
While mass is usually written g/mol, is the ratio mol/g also acceptable?
Yes but you just have to adjust in your math to where units cancel out
Calculate and compare subatomic particles that make up: 19O, 16O, 17O, 19F, 16F, 238U, 240U
19O = 8p, 11n, 8e 16O = 8p,8n,8e 17O = 8p, 9n, 8e 19F = 9p, 10n, 9e 16F = 9p, 7n, 9e
The valence electron in a lithium atom jumps from energy level n = 2 to n = 4. What is the energy of this transition in joules? in eV?
E = Rh [1/ni2 - 1/nf2] = 2.18 x 10^-18 [1/2^2 - 1/4^2] = 2x10^-18[3/16] = 3.75x19^-19J
E = Rh [1/ni2 - 1/nf2] = 13.6 [1/2^2 - 1/4^2] = 14(3/16) = 2.5eV
If an electron emits 3eV of energy, what is the corresponding wavelength of the emitted photon?
400nm (check p. 36 of book)
Calculate the energy of a photon of wavelength 662nm
3.00 x 10^-19J (check p. 36 of book)
Planck’s constant? and what did he propose?
He developed first quantum theory proposing that energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta. the energy of a quantum is given by his relationship E = hf where h is known as planck’s constant 6.626 x 10^-34 Js
- f is frequency of radiation
what is speed of light
3.00 x 10^8 m/s
Hund’s rule?
within a given subshell, orbitals are filled such that there are a maximum umber of half-filled orbitals with parallel spins
paramagnetic and diamegnetic
paramagnetic = magnetic field will cause PARAllel spins in unpaired electrons and cause an attraction
diamagnetic = atoms that have only paired electron and will be slightly repelled by a magnetic field
If given the following quantum numbers, which element do they likely refer to? n = 2, l =1 n = 3, l = 0 n = 5, l = 3 n = 4, l = 2
- B, C, N, O, F, Ne
- Na, Mg
- actinide series
- Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd
Write out and compare an orbital diagram for a neutral oxygen atom and an O2- atom
write it out
MRA is a technique that can resolve defects like stenotic (narrowed) arteries. A contrast agent like gadolinium or manganese injected into the blood stream interacts with the strong magnetic fields of the MRI device to produce such images. Based on their orbital configurations, are these contrast agents paramagnetic or diamagnetic?
Both of these molecules have an unfilled valence electron shell with relatively less paired electrons THEREFORE they are paramagnetic
What is the modern periodic table arranged by?
atomic number
Based on their locations on the periodic table, identify a few elements that likely possess: luster, poor conductivity of heat and electricity, good conductivity but brittle
luster: metals
poor conductivity of heat and electricity: nonmetals
conductivity but brittle: metalloids
Which elements are metalloids?
B, Si, Ge, As, Sb, Te, Po, At
Which has a larger radius?
F or F-
K or K+
Anions are bigger
F- and K
Rank the following elements by DECREASING first ionization energy: Ca, C, Ge, K
(most to least)
C > Ge > Ca > K
Rank the following by increasing electron affinity: Ba, Cu, S, Y
Ba < Y < Cu < S
rank by decreasing electronegativity: Sb, Ne, O, Tl
O > Sb > Tl > Ne
increasing atomic radius: Nb, Pr, Ta, Xe
Xe < Nb < Ta < Pr
Write down the groups of the periodic table that exhibit:
- high reactivity to water
- six valence electrons
- contain at least 1 metal
- multiple oxidation states
- negative oxidation states
- possess a full octet in the neutral state
- high reactivity to water = groups 1 and 2
- six valence electrons = group 6 and 16
- contain at least 1 metal = groups 1 through 15
- multiple oxidation states = all groups; most notably groups 3-12 transition metals
- negative oxidation states = almost all groups; most notably 14-17 nonmetals
- possess a full octet in the neutral state = noble gasses
Describe the atomic differences between ionic and covalent compounds:
ionic = involve gain or loss of electrons covalent = electrons shared between 2 atoms
List 3 elements that violate octet rule and why
H - only has 1 electron
He - only has 2
Li, Be, or B
period 3 or greater
which periodic trend determines whether a covalent bond is polar or nonpolar?
electronegativity
Why do ionic bonds tend to form between nonmetals and metals?
Metals lose electrons bc they have LOW ionization energies while nonmetals gain electrons because they have HIGH electron affinities.
describe 5 characteristics of ionic compounds
- high melting and boiling points due to electrostatic attractions
- solubility of ions in water due to interactions with polar solvents
- good conductors of heat and electricity
- crystal lattice arrangement to minimize repulsive forces
- large electronegativity differences between ions
Describe the relationship between bond strength, bond length, and bond energy
bond strength: electrostatic attraction between nuclei and electrons; multiple bonds (higher bond order) increases strength
bond length: consequence of the attractions of bond strength; the STRONGER the bond, the SHORTER it is
bond energy: minimum amount of energy required to break a bond; the stronger the bond, the higher the bond energy
For what values of ΔEN will a nonpolar covalent bond form? polar covalent? ionic?
nonpolar covalent = 0 to 0.5
polar covalent = 0.5 to 1.7
ionic = 1.7 or higher
Predict the molecular geometry of: PCl5 MgF2 AlF3 UBr6 SiH4
PCl5 = trigonal bypyramidal MgF2 = linear AlF3 = trigonal planar UBr6 = octahedral SiH4 = tetrahedral
Rank the major IMFs strongest to weakest:
hydrogen bond > dipole-dipole > van der Waal/dispersion
Describe what occurs during dipole-dipole interactions
A dipole consists of a segment of a molecule with partial positive and partial negative regions. The + end of one molecule is attracted to the - end of another
In order to exhibit hydrogen bonding, what must be true of a given molecule?
it must have Nitrogen, Oxygen, or Fluorine
