Chapters 7 and 8 Flashcards
The quantum numbers resulted from the…
Pauli exclusion principal (two electrons must have opposite spins if they occupy the same orbital)
Nuclear charge is based on the fact that….
electrons are both attracted to the nucleus and repelled by other electrons
Z eff = ____ - _____
Z (atomic #) - S (shielding/# of core electrons)
Effective nuclear charge is the net charge experienced by….
a particular electron in an atom resulting from a balance of the attractive forces of the nucleus and the repulsive forces of other electrons
Z eff is the charge experienced by the _____ electrons
outermost
High Z eff vs lower Z eff
The higher effective nuclear charge has a smaller atomic radius, a higher IE, and a higher electronegativity (periodic trends)
In the hydrogen atom 2s and 2p subshells have the ____ energy, but in atoms with more than two electrons the energies are ____
same different
States that lower energy orbitals fill first (predicts arrangement of electrons)
Aufbau Principal
Degenerate orbitals (those of the same energy) are filled with electrons until all are half filled before the pairing up of electrons can occur
Hund’s Rule
What is the basis of the Hund’s rule?
It results in the most stable arrangement of the electrons
When calculating effective nuclear charge (slaters law) it is best to write the electron configuration first and then….
group it together by increasing n
4f block of the periodic table
lanthanides
5f block of the periodic table
actinides
Exceptions when writing electron configurations occure when…
you get to d4 and d9 electron configurations
For example:
4s^2 3d^4 becomes 4s^1 3d^5
4s^2 3d^9 becomes 4s^1 3d^10
To form a cation, the highest n electron is removed first for example…
Iron (Ar)3d^6 4s^2 becomes Iron (Ar) 3d^6 + 2e-
How do we know the configurations of ions?
By their magnetic properties
Paramagnetic
has unpaired electrons (attracred to a magnetic field)
Diamagnetic
has all paired electrons (not attracted to a metal field)
Ferromagnitism
when the spins of unpaired electrons in a cluster of atoms/ions align themselves in the same direction even without a magnetic field
Orbital energies_____as Z* increase
drop
distance betweeen two nuclei
bond distance (half of this equals the covalent radius, which is usually in picometers)
Ionization energy is always a _____ value
positive
Ionization energy is….
the energy required to remoced an electron from an atom in the gaseous phase
The _____ to the nucleus an electron is, the higher the ionization energy
closer
Electron affinity is….
the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion
Noble gase have _____ affinity for electrons
no
EA (ΔU) is the energy released when an electron attached to a gas-phase atom to form an anion
Compared to EA, ΔU…
Is equal in magnetude, but opposite in sign
EA= -ΔU
Anion>Atom>Cation
Why?
Smaller Cation:
Same amount of attractive forces from protons are exerted over less electrons, so the electrons are drawn closer to the nucleus
Larger Anion:
Increased electron-electron repulsion (more electrons than protons)
Isoelectronic
Same number of electrons, different number of protons
Metallic character
How readily an atom can lose an electron
Periodic trends from over and up
Atmoic radius: decreases
Metallic character: decreases
Electron affinity: increases
IE: Increases
Electronegativity: Increases
Electron attachment enthalpy
Electron Affinity = -ΔH
Covalent bond
sharing of valence electrons between atoms (non-metal to non-metal)
also responsible for the atom-atom connections in polyatomic ions
Ionic bond
Electrostatic in nature, complete transfer of electrons from a metal to a non-metal (cation + anion)
Metallic bond
attractive forces holding pure metals together, cations are in a “sea” of electrons
Core electrons (are or are not?) involved in bonding or chemical reactions
Are not
Introduced the Lewis Dot Structure
Gilbert Newton Lewis
Octet rule
a chemical rule of thumb that reflects observation that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas (stable configuration)
Exceptions to the octet rule/don’t obey octet rule
- More than 4 bonds/8 electrons (expanded octet)
- Odd number of electrons
When drawing a lewis dot structure which atom is the central atom?
The least electronegative
When drawing the lewis dot structure for an acid, where does the H+ go and why?
It is placed on the outside because acids want to donate the H+ ion, which allows for easy removal
Oxoacid
An acid containing oxygen
Exceptions to Lewis Dot Structures (NASL)
N = 8 for all elements except…
H, He =2
Be = 4
B = 6
isostructural
same structure
Formal charge is calculated by…
FC = VE - (LP + 1/2 BP)
(+) FC…
(-)FC
contributes more e- than it receives
gets more e- than it receives
A formal charge of 0 means that specific lewis dot structure is…
more favored, more stable
Resonance structures are not seperate structures they are actually…
hybrid/composite structures (not alternating back and forth between the different structures)
Resonance _____the energy by distributing electron density over the entire molecule
stabilizes/lowers
coordinate covalent bond
when a bonding pair of e- originates on one of the bonded atoms (just short of fulfilling octet)
free radicals have _____ electrons
unpaired
Atoms from the _____period or __ block and beyond can have an expanded octet
3rd
d
Bond angles aren’t exact because…
the more lone pairs there are, the more pushed together the atoms are, which results in a slightly smaller bond angle
Strengths of repulsion
lone-lone > lone-bond > bond-bond
Molecular geometry vs electron-pair geometry
molecular is more general while electron-pair is more specific and takes the lone pairs into account
equatorial positions
lie in the imaginary sphere around the central atom
(lone pairs prefer to occupy this space because there is more room)
axial position
north and south poles of the atom
Which EPG has no axial or equatorial postions?
Octahedral
Electronegativity
a measure of the tendency of an atom to attract a bonding pair of electrons
Electronegativity is measured on the_____scale
Pauling
Example of a pure covalent bond
(difference of 0 in electronegativities)
C-C
Positive and negative ends amount to a ____ bond
polar
Difference of 0.1 to 0.3 in electronegativity
non-polar covalent
Difference of 0.4 - 1.7
Polar covalent
Difference of 1.8 and beyond
Ionic
All homonuclear (composed only of the same element) diatomic molecules are…
non-polar
dipole moment
(automatically makes a molecule polar)
the magnitufe of charges multiplied by the distance (net dipole)
μ = q (charges) * d (distance)
Units of coulomb meters or debyes
The greater the difference in electronegativities the more _____the bond
polar
bond length
distance between the nuclei of two bonded atoms
energy required to break a covalent bond (in the gas phase)
bond dissociation enthalpy
ΔHr = …
bonds broken - bonds formed
