Unit 4 - light and electron trends Flashcards
4 characteristics of waves
Amplitude, wavelength, frequency, speed
amplitude
the height of the waves from the orgin to the peak or crest. this adjusts brightness or intensity of the light - not the type of light itself
wavelength (λ)
the distance from peak to peak (determines the type of light)
frequency (v)
how fast the wave oscillates (determines the type of light), measured in hz, 1/s
speed
the speed of light is constant
formula: 3.00x10^8 m/s
~~~
long wavelength, low frequency, low energy
what is the relationship between wavelength (λ) and frequency (v)
inverse
^^^
short wavelength, high frequency, high energy
formula for wavelength and frequency
speed of light = (wavelength) (frequency)
c=λv
λ - meters
v - 1/s
how would you find the frequency of red light that has a wavelength of 650nm
1 - convert nm to m
2 - plug into the formula v=c/λ
what is the relationship between energy (E) and frequency (v)
direct
which has a shorter wavelength - red or violet light?
violet
formula for energy and frequency
Energy = (Plank’s constant)(frequency)
E = hv
h - plank’s constant
v - 1/s
as the wavelength gets longer, does the frequency get higher or lower?
lower
as the frequency increases, does the energy increase or decrease?
increase
which has a higher frequency - red light or violet light
violet
which is more energetic - red or violet light?
violet
what do you see when you look at sunlight through a spectroscope?
a rainbow/all of the colors (ROYGBIV)
what gas is inside a fluorescent lightbulb
mercury
T or F - every element has its own emission spectra
T
gravitational potential energy
since gravity attracts an object towards earth, an object will store potential energy depending on its height above earth
Electric potential energy
since opposite charges attract (by the electrostatic force), an electron can have stored potential energy depending on how close the electron is to the nucleus
what is potential energy converted into
light
Bohr model of the atom
in an atom, electrons can only exist in distinct energy levels. this means that the energies of the electrons in atoms are quantized
using the emission spectrum of hydrogen, Neils Bohr was able to determine the specific discrete energies that are possible for a single electron to have when in a hydrogen atom
quantized
the possible number of energy values of an electron are negative, electrons reside on specific energy levels
what happens to the electron in hydrogen when electricity is sent through hydrogen gas
1 - the electrons absorb energy from the electricity and they jump up to a higher energy level, gaining potential energy
2 - since the electron is attracted to the nucleus by electrostatic force, the e- falls back down to a lower energy level and releases energy in the form of light
what attracts electrons to the nulceus
electrostatic force
since electrons are attracted to the nucleus, it is relatively difficult to move an e- further away from the nucleus. Thus, when an electron does not move further away from a nucleus, energy must be…
absorbed by the electron
when an electron moves further away from the nucleus, the electron must…
gain potential energy
what happens to electrons when they absorb energy
they jump to a higher energy level, gaining potential energy. then, the electrons will be attracted to the nucleus through electrostatic force, thus releasing energy in the form of visible light (specifically a photon of light)
orbitals
electrons do not “orbit” in a defined path around the nucleus. Instead, for a particular energy electron, one can only know the most probable locations to find the electron. Thus, we say that electrons are in orbitals.
describe the S orbital
1 orientation, spherical shape
describe the p orbital
3 orientations (aligned on x, y, and z axis), peanut shape
describe the d orbital
5 orientations (along different planes), four-leaf clover shaped
describe the f orbital
7 orientations, shape has 8 lobes (flower shaped)
overlap of sublevels
as one goes up, the energies of the energy levels get closer and closer to each other. thus, the energy levels overlap more and more as one goes up
order of sublevels
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s
Aufbau principle
fill the lowest energy level first
pauli exclusion principle
there can be a maximum of only 2 electrons per orbital with opposite spins
why are electrons represented by arrows when writing electron configuration
because they spin clockwise and counterclockwise
Hund’s rule
when filling a sublevel, there should be a maximum number of unpaired electrons before pairing them up
shielding effect
more shielding e-‘s block the valence e-‘s from feeling the positive pull of the nucleus while Zeff remains the same
what is Zeff
effective nuclear charge
the Zeff is the amount of positive charge that is effectively attracting the valence electrons
octet rule
atoms will lose, gain, or share e-‘s in order to have 8 in the outer shell
Atom size vs. Ion Size
atom is less than negatively charged ion
atomic size:
as you move across the periodic table, atomic size generally decreases
positive ionic size:
these atoms have lost e-‘s, resulting in a positive charge. typically SMALLER than their parent atoms because losing e-‘s reduces the amount of shielding e-‘s and allows remaining e-‘s to be pulled closer to the nucleus
negative ionic size:
these atoms have gained e-‘s, resulting in a negative charge. typically LARGER than parent atom because gaining e-‘s increases the # of shielding e-‘s, thus reducing Zeff
what is ionization energy
the amount of energy needed to remove an e- from an atom
why does ionization energy decrease moving down a family/column
it will be easier to remove an electron because it gets further from the nucleus, thus the Zeff decreases. therefore, the IE decreases as well because it will be easier to remove an e-
why does the IE increase moving across a period
the IE will increase because the radius of the atom decreases and the valence e- gets closer to the nucleus. Thus, the e- will be harder to remove and the IE will increase.
which element has higher ionization energy - C or O
O
which element has higher ionization energy - Na or K
K
do metals or non metals have higher ionization energy
nonmetals
what is meant by a second or third ionization energy / successive ionization energy
the shielding e-‘s become the new valence e-‘s and the size of the atom decreases. Thus, the IE is stronger and the e- is harder to remove from the atom.
why do noble gasses have particularly high ionization energies
the valence e-‘s are closer to the nucleus and they have a “full outer shell”
what is electronegativity
electronegativity is the relative tendency of an atom to attract electrons towards itself from another atom in a bond
if an atom has high electronegativity, the atom _______ attracts electrons
strongly
why does electronegativity decrease moving down a family
there are less shielding e-‘s in the smaller atom, therefore it will strongly attract e-‘s.
why does electronegativity increase when moving across a period
as they move across the periodic talbe, atoms get smaller and there are less shielding e-‘s in the atom. therefore, it will strongly attract e-‘s.
in general, which have higher electronegativities (metals or non-metals)
nonmetals
if Na and Cl bonded together to make NaCl, which atom would attract the e-‘s more strongly
Cl
which elements have the three highest electronegativities
F O N (especially F)
if Mg and O bonded together to make NaCl, which atom would attract the e-‘s more strongly
O
which has the smaller radius
F or F-
Na of Na+
Ca or Ca+2
N or N-3
F-
Na
Ca
N-3
which elements tend to lose e-‘s and form positive ions and why
metals (metals are LOSERS)
describe the process of fluorescence
Excitation: A material absorbs a photon and transitions from its ground state to an excited state.
Fluorescence lifetime: After a brief period, the material returns to its ground state, emitting a photon with lower energy.
Emission: The emitted photon has a different frequency, resulting in the characteristic fluorescent glow
what is phosphorescence
“glow in the dark”
the electrons are able to absorb energy quickly and lose it slowly as they fall back down to ground state
what is triboluminescence
Charge Separation: When a material is mechanically stressed, its surface can become electrically charged due to the triboelectric effect. This effect occurs when two materials come into contact and then separate, causing electrons to transfer from one material to the other.
Electrical Discharge: The separated charges can create an electrical discharge when they reunite. This discharge can ionize nearby gas molecules, causing them to emit light.
Energy Release: The mechanical action can also give electrons energy, and when these electrons return to a more stable state, they release light.
the crystals tend to break on a plane with one side of negative particles and one side of positive particles. When a crystal is broken, negative charges bridge the gap between the two planes. The electrons primarily emit energy in the form of UV light.
