Ch 1 - Anatomic Structure Flashcards
Where are protons found?
How do they relate to the atomic number of an element?
In the nucleus
Atomic number (Z) of an element is the number of protons present!
Atomic number is the top number in the periodic table
Where are neutrons found?
How do they relate to atomic mass / MASS NUMBER?
In the nucleus
Atomic mass / MASS NUMBER (A) is the number of protons plus the number of neutrons.
What are isotopes?
An element can have a variable number of NEUTRONS.
Isotopes share the same atomic number (# of electrons) but have different mass numbers.
Where are electrons found?
What are some properties of electrons?
Electrons are in the space surrounding the nucleus.
Weigh very little (1/2000 of a proton)
Electrostatic force of attraction (eg being repelled) is far greater than the gravitational pull.
Energy levels based on electrons distance from the nucleus:
Closer to nucleus: lower energy Further out (in higher shells): higher energy
What are valence electrons?
What do they determine?
Electrons that are in the shell furthest from the nucleus
These have the strongest interactions with the environment, and weakest interactions with the nucleus.
They determine the REACTIVITY of an atom.
What are anions and cations?
Negatively (anion) and positively (cation) charged atoms.
Happens when electrons are gained and lost
What is the difference between atomic MASS and atomic WEIGH?
Which one is reported on the atomic table?
Atomic MASS is the number of protons plus the number of neutrons. (Varies from one isotope to another)
Atomic WEIGHT is constant. It represents the WEIGHTED average of the isotopes.
ATOMIC WEIGHT is on the atomic table.
Why use atomic weight?
2
Gives the mass of the “average” atom of that element
Gives the mass of one “mole” of the element in grams.
What is a “mole”?
How does it relate to atomic weight?
A number of things (atoms/ions/molecules) that equal to Avogadro’s number.
NA= 6.02 X 10^23
Ie:
The average carbon atom has a mass of 12 amu
6.02 X 10^23 Carbon atoms have a combined mass of 12g
What is the equation for Planck Relation?
Developed by Max Planck, it is the first quantum theory.
E = hf
E = energy of a quantum h = planks constant (6.626 X 10^-34 J) f = frequency of radiation
What are quanta?
Electromagnetic radiation from matter. Quanta are the discrete bundles that it comes in.
What is the formula for angular momentum?
L = nh
2 (pi)
n = principal quantum number h = Plancks constant
BECAUSE the only variable is the principal quantum number, the angular momentum of an electron changes in discrete amounts with respect to that number. (Increase n = increase in L)
*BOHR
What is the formula for energy of the electron?
E = _ Rh
n^2
Rh = rydberg unit of energy (2.18 X 10^-18 J/electron )
n = quantum number
As n increases, E becomes closer to zero (increases too - becomes less negative)
**BOHR
How does the energy of an electron change as it gets further away from the nucleus?
(Relating to the “energy of the electron” formula)
It’s energy INCREASES - becomes less negative.
Increasing n value
What are changes in quantum values like - discrete of infinite?
DISCRETE - only allow certain changes, in intervals.
What is the ground state of an atom?
What is it the opposite of?
The state of lowest energy
All the electrons are at the lowest possible orbitals
Opposite of an “excited state” where at least one electron is in a subshell of higher than normal energy.
Are atoms usually in the ground state or the excited state - why?
Usually in the GROUND STATE
To minimize energy
When subjected to extreme heat or irradiation, may become excited.
What do electrons do as they move from lower energy to higher energy?
AHED
A - absorb light
H - higher potential
E - excited
D - distant (from nucleus)
What happens after brief period of excitation?
How does it relate to Planck’s relation?
The atoms will return to the ground state rapidly, causing an emission of discrete amounts of ENERGY in the form of PHOTONS.
(The energy emitted is the Planck relation formula, E = hf aka the energy of a quantum!!!)
What is the equation for electromagnetic energy of a photon?
E = hc
(Wavelength)
h = Plancks constant c = speed of light in a vacuum (3.0 X 10^8 m/s)
The shirt yet the wavelength, the higher the electromagnetic energy.
What is an atomic emission spectrum?
Each atom’s electrons can only be excited to distinct energy levels, which creates a unique atomic energy spectrum.
The spectrum is composed of light at certain frequencies. (Line spectrum)
For a hydrogen atom, what is the emission spectrum like - name the different “series”:
- LYMAN SERIES
From n=2 or greater to n=1
(From really far to the first shell) - BALMER SERIES
from n=3 and greater to n=2 - PASCHEN SERIES
From n=4 or greater to n=3
Equation to calculate the energy associate with changes from one shell to another (ie creation if a photon through movement to ground state)
E = hc = _ Rh x 1 _ 1
(wavelength) Ni^2 Nf^2
This equation looks at initial minus final energy (the n’s)
The energy of the emitted photon corresponds to the difference in energy between the higher-energy initial state and the lower-energy final state
Positive E value = emission
Negative E value = absorption (excitement)
What are protons, neutrons, and electrons?
What do they weigh?
Proton - positively charged (+1 atomic mass unit)
Electron - negative charge (weighs almost nothing)
Neutron - no charge (1 atomic mass unit)
What is the quantum mechanical model?
Atoms fitness travel in defined orbits but are rather localized in ORBITALS (a region of space around the nucleus)
Heisenberg uncertainty principle
It’s impossible to know both an electrons position and it’s momentum EXACTLY at the same time
What is a quantum number?
4 numbers which can completely describe any electron in an atom
- Principal
- Azimuthal
- Magnetic
- Spin
The principal quantum number (n)
Describes the average energy of a shell
Max # of electrons per shell:
2n^2
The azimuthal quantum number (l)
Described the subshells within a given principal level of energy (s, d, p, or f)
Max number of electrons per subshell:
4l+2
Magnetic quantum number (m_l)
Specifies the particular orbital within a subshell where an electron is likely to be found at any moment
Subshells: 1s - small circle 2s - large circle 2px - 2 small circles on x axis 2py - large circles overlap 2pz - 2 s circles on y axis
The spin quantum number (m_s)
Indicated the spin orientation (plus or minus 1/2) of an electron in an orbital
Two electrons in the same orbital must have opposite spins (“paired”)
Electrons in diff orbitals with the same spin are called “parallel” spins
How is electron configuration annotated?
(Orbital)^(number electrons)
L and m values if quantum numbers combine to designate which orbital
Ie: 1s^2 2s^1 2p^2
2 electrons in 1s, 1 in 2a, and 2 in 2p
What is the “building up” principle in terms of electrons and orbitals?
Aka Aufbau principle
Electrons fill from lower to higher subshells
What is the n+l rule?
Can be used to rank subshells by increasing energy
The lower the sum of n+l values, the lower the energy of the subshell
If the number is the same for two, the one with the lower “n” will be of lower energy and fill with electrons first
What is spectroscopic annotation for every subshell on the periodic table?
Assigning subshells s, p, d, and f to the periodic table.
(Where l is the azimuthal quantum number) S means l=0 P means l=1 D means l=2 F means l=3
So for an element in 2p, l=1 and n=2
What is hund’s rule?
Subshells with multiple orbitals (p, d and f) fill electrons so that every orbital in a subshell gets one electron before any of them get a second
Paramagnetic materials - what are they?
Have unpaired electrons that align with magnetic fields, attracting it to a magnet
dimagnetic materials - what are they?
Materials that have all paired electrons, which cannot easily be realigned. These are repelled by magnets
What are valence electrons?
Electrons in the outer shell which are available for bonding with other atoms.
Atoms typically interact with each other to try and complete an octet in the valence shell
Where on the periodic table are paired versus unpaired electrons ?
Unpaired electrons tend to be on the Left side (beginning of a block) and paired electrons on the Right (end of a block)
Reminder: paired electrons: paramagnetic. Unpaired electrons: diamagnetic
