Ch 1 - Atomic Structure Flashcards
What is the charge and mass of a proton?
\+1 1 amu (atomic unit charge)
What is the atomic number?
Z
- equal to the number of protons found in an atom of that element
What is the charge and mass of a neutron?
- charge of 0
- about 1 amu; mass is slightly larger than a proton and together they make up almost the entire mass of an atom
What is a mass number (atomic mass)?
A
- the sum of the protons and neutrons in the atom’s nucleus
What are isotopes?
atoms that share an atomic number but have different mass numbers (different number of neutrons)
What are electrons? What is their charge?
- move through the space surrounding the nucleus and are associated with varying levels of energy
- charge of -1
How do the electrostatic and gravitational forces of attraction react in relation to protons and electrons?
because subatomic particles’ masses are so small, the electrostatic force of attraction between the unlike charges of the proton and electron is far greater than the gravitational fore of attraction based on their respective masses
What are electron shells and what determines their energy levels?
- electrons move around the nucleus at varying distances, which correspond to varying levels of electrical potential energy
- electrons closer to the nucleus are at lower energy levels and electrons in higher electron shells have higher energy levels
What are valence electrons?
- electrons that are farthest away from the nucleus with the strongest interactions with the surrounding environment and the weakest interaction with the nucleus
- more likely to become involved in bonds with other atoms because they experience the least electrostatic pull from their own nucleus
What is the difference between a cation and anion?
- cation: positively charged atom, loss of electron
- anion: negatively charged atom, gain of electron
When do the number of protons equal the number of electrons?
in a neutral atom
What is the atomic weight?
- the weighted average of the different isotopes of an element
- the number reported on the periodic table
What is Avagadro’s number?
NA = 6.02 x 10^23/mol
What is quantum?
energy difference between energy levels first described by Planck
How is the energy of quantum determined?
E=hf (Energy = Plank’s constant x frequency)
What is quantization?
- there is not an infinite range of energy levels available to an electron; electrons can exist only at certain energy levels
- the energy of an electron increases the farther it is from the nucleus
What is angular momentum of an electron?
Bohr’s model
L = (nh)/(2pi)
the angular momentum changes only in discrete amounts with respect to the principal quantum number
How did Bohr calculate the energy of an electron?
E = -Rh/n^2
Rh (Rydberg unit of energy) = 2.18 x 10^-18 J/electron
- energy of an electron changes in discrete amounts with respect to the quantum number
- the energy of an electron increases the farther out from the nucleus that it is located (increasing n)
What is the difference between a ground state and an excited state?
- ground: state of lowest energy where all electrons are in the lowest possible orbitals
- excited: when at least one electron has moved to a subshell of higher than normal energy
What happens to electrons as they go from a lower energy level to a higher energy level?
AHED
- Absorb light
- Higher potential
- Excited
- Distant (from nucleus)
How can electrons be excited and how long do they stay excited?
- by heat or other energy forms
- brief lifetime causing electrons to go back to ground state causing emission of energy in the form of photons with a specific wavelength
How can the electromagnetic energy of a photon be determine?
E = hc/lambda
What is the line spectra?
- spectrum of light at specific frequencies where each line on the emission spectrum corresponds to a specific electron transition
What is an atomic emission spectrum?
- different to each element since each require different amount of energy to return to ground state from excited (photon emitted)
- can be used as a fingerprint for the element
What is the difference between the Lyman, Balmer, and Paschen series?
- lyman: the group of hydrogen emission lines corresponding to transitions from energy levels n>=2 to n=1 (larger energy transitions, shorter photo wavelengths)
- balmer: energy levels n>=3 to n=2
- paschen: n>=4 to n =3
What is the equation for energy when Bohr and Plank are combined?
E = -R(1/ni^2 - 1/nf^2)
the energy of the emitted photon corresponds to the difference in energy between the higher-energy initial state and lower energy final state
- +E emission, -E absorption
What is absorption spectra?
exciting the electrons of a particular element to jump from lower energy level to higher results in energy absorption at specific wavelengths (photon absorbed)
What is Heisenberg uncertainty principle?
it is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron
What is Pauli exclusion principle?
no 2 electrons in a given atom can posses the same set of 4 quantum numbers
What is the principal quantum number?
- n
- any positive integer value
- the larger n, the higher the energy level and radius of the electron’s shell
What is the maximum number of electrons within a shell? What is the relationship between shell distance and energy?
2n^2
- the difference in energy between 2 shells decreases as the distance from the nucleus increases
What is the angular momentum number?
- l = 0 –> n-1
- refers to the shape and number of subshells within a given principal energy level
What is the spectroscopic notation?
s –> l=0 (2 electrons)
p –> l=1 (6 electrons)
d –> l=2 (10 electrons)
f –> l=3 (14 electrons)
What is the maximum number of electrons within a subshell?
4l+2
What is the magnetic quantum number?
- ml = -l –> +l
- specifies the particular orbital within a subshell where an electron is most likely to be found at a given moment in time
What is the spin quantum number?
- ms = +/- 1/2
- whenever 2 electrons are in the same orbital, they must have opposite spins (paired)
- electrons in different orbital with the same ms value (parallel spins)
What is the electron configuration?
- for a given atom or ion, the pattern by which subshells are filled, as well as the number of electrons within each principal energy level and subshell using spectroscopic notation
What is Aufbau principle?
- electrons fill from lower to higher energy subshells
- each subshell will fill completely before electrons begin to enter the next
What is Hund’s rule?
within a given subshell, orbitals are filled such that there are a maximum number of half-filled orbitals with parallel spins (crowded bus)
What are the 2 exceptions to Hund’s rule?
half filled and fully filled orbitals have lower energies (higher stability) than other states
- Cr (z=24) [Ar] 4s13d5 making d shell half filled and more stable
- Cu 9z=29) [Ar]4s13d10 making d shell full and more stable
What is the difference between paramagnetic and diamagnetic?
- para: materials composed of atoms with unpaired electrons will orient their spins in alignment with a magnetic field, and the material will thus be weakly attracted to the magnetic field
- di: materials consisting of atoms that have only paired electrons will be slightly repelled by a magnetic field
What are the 3 isotopes of hydrogen?
- protium
- deutrium
- tritium
What did Rutherford do?
first postulated that the atom had a dense, positively charged nucleus that made up only a small fraction of the volume of the atom
What is Bohr’s model?
a dense, positively charged nucleus is surrounded by electrons revolving around the nucleus in orbits with distinct energy levels
Which orbital are valence electrons found for each group?
- for representative groups (group 1-2 and 13-18), s and/or p orbitals
- for transition groups, s and either d or f orbitals
Where are electrons removed from when forming a cation?
from the subshell with the highest n value (s)
