Chapter 5: Electronic Structure of Atoms and Ions Flashcards
Z
- atomic number (number of protons)
r
- distance between the particles (usually the nucleus and the electron)
how does r affect the potential energy of the system (4)
- as r decreases, potential energy (V) increases
- forces are stronger at shorter distances and weaker at longer distances
- between oppositely charged particles the forces are attractive and the lowest (most negative) potential energies will occur at short distances (small r)
- between similarly charged particles, the forces are repulsive and the lowest potential energies will occur at long distances (big r)
radial component of a wavefunction
- R(r): depends only on r and describes the size of the orbital
angular component of a wavefunction
- Y(θ,φ): a function of only the angles φ and θ and corresponds to the shape of the orientation of the orbital
what is the wavefunction for a one-electron species?
atomic orbitals:
ψ(r,θ,φ) = R(r)Y(θ,φ)
n
- principal quantum number
- 1, 2, 3…
- each value is a “shell”
l (L)
- angular momentum quantum number
- 0 < l < n-1
- each value is a “subshell”
m(sub l)
- magnetic quantum number
- l < m < l
l subshells
- 0 = s
- 1 = p
- 2 = d
- 3 =f
potential energy equation
- V(r)= -Z/r
- V(r)= q(1)q(2)/r
what is each quantum number described by
- three quantum numbers: n, l and m
how many orbitals are there in the nth shell
- n^2 orbitals
how many nodes does an orbital have
- (n-1): (# of total nodes = # angular nodes + # radial nodes)
how many orbitals are there for each value of n
- 2L+1 orbitals
how does Z affect the radial probability distribution
- bigger Z means the distributions probability is closer to the nucleus of the atom
What are the deficiencies of the Bohr model? (4)
- Bohr model does not align with the peak nor the average radial distance as given by quantum mechanics
- Bohr orbits violate the uncertainty principle because they predict the electrons to be at a specific distance with a specific momentum
- Bohr atoms are flat, like a solar system, and do not account for experimental observation that atoms are spherical
- the Bohr model, even with extensions, cannot describe a multi-electron atom
Why should we not use the Bohr model?
- the Bohr model is fundamentally flawed and should not be used to describe the nature of atoms and ions or to rationalize chemical phenomena
What are the characteristics of the p orbitals? (2)
- L=1
- they have one angular node
nodal planes
- angular nodes that exist as planes on the Cartesian coordinate system
What is the trend for p orbitals?
- as n increases, distributions and most probable radial distances shift to larger r: there is a greater possibility of finding the electron further from the nucleus
What are the three p orbitals?
- p_x
- p_y
- p_z
What are the five d orbitals?
- d_xy
- d_xz
- d_yz
- d_x^2-y^2
- d_z^2
What are the characteristics of the d orbitals? (2)
- L=2
- 2 angular nodes