Chapter 1 - Atomic Structure Flashcards
Where are protons and neutrons found?
In the nucleus
Each proton has an amount of charge equal to what?
The fundamental unit of charge
e = 1.6 x 10^-19 Coulombs
Simplified as “+1e” or even “+1”
Protons have a mass of approximately what?
One atomic mass unit (amu)
What are elements defined by?
The number of protons they contain
All atoms of a given element have the same atomic number but may not contain the same mass, why is this?
Because they can have varying number of neutrons
The atomic number is what sign in chemistry?
Z
How much more does a neutron weight than a proton?
Not much at all, slightly greater in weight
Why do protons and neutrons in the nucleus make up almost all the mass of an atom?
Because the electron is of negligible weight
Mass number is given what sign in chemistry
A
What is the mass number (A)
It is the sum of protons and neutrons in the atoms nucleus
What are isotopes?
Atoms that share the same atomic number hence are the same element but have different mass numbers due to varying number of neutrons
In a written equation where is the atomic number (Z), mass number(A), and atom (X)?
The atom is after the atomic number and mass number, the atomic number being below the mass number which is on top
How does an electrons charge compare to a proton?
Their charge is equal in magnitude but in opposition of each other 1:1
The mass of an electron is approximately how much of a proton?
1/2000
Since masses of subatomic particles are so small, what does this mean for electrostatic force and gravitational force?
The electrostatic force of attraction between the unlike charges of the proton and electron is far greater than the gravitational force of attraction based on their respective masses
Why do electrons have varying levels of electrical potential?
Because they move around the nucleus at varying distances
Which electrons have lower and higher levels of energy?
Electrons closer to the nucleus are at lower levels of energy, those further have higher levels of energy
What electrons have the strongest interactions with the surrounding environment and the weakest interactions with the nucleus?
The electrons that are furthest from the nucleus, these electrons are called valence electrons
What electrons are much more likely to become involved in bonds with other atoms and why?
Valence electrons, because they have the least electrostatic pull from their own nucleus
Generally speaking What determines the reactivity of an atom?
Valence electrons
How do valence electrons play a role in increasing stability?
They can share or transfer valence electrons in bonds allowing elements to fill their highest energy levels to increase the stability
What is a positive and negative charged atom called?
Positively charged - cation
Negatively charged - anion
Atomic mass unit (amu) is equal to what?
1.66 x 10^-24g
What is the difference between Atomic weight and atomic mass
Atomic weight is the average mass of all isotopes of an element
Atomic mass refers to the mass of an individual atom of a specific isotope of that element
Is the atomic weight or atomic mass on the periodic table?
Atomic weight
What is a mole?
A mole is a unit of measurement used to quantify the amount of a substance
It represents 6.02 x 10^23 (Avogadro’s number)
What did Ernest Rutherford provide experimental evidence of in 1910?
That an atom has a dense, positively charged nucleus that accounts for only a small portion of the atoms volume
What did max Planck do in 1900?
He developed the first quantum theory, proposing that energy emitted a electromagnetic radiation from matter comes in discrete bundles called quanta, energy of quantum, given by the Planck relation
What is the Planck relation formula?
E = hf
E - energy of a photon
h - plancks constant = 6.626 x 10^-34 J•s
f - frequency of radiation
In 1913, danish physicist Neil’s Bohr used the work of Rutherford and Planck to develop his model of the electronic structure of the hydrogen atom called what?
The Bohr model
What is the equation for angular momentum when the object is moving in a circle around a fixed axis like an electron is?
L=mvr
L=angular momentum
m=mass
v=linear velocity of object
r=distance between object and the axis of rotation
What is the equation for kinetic energy?
K=1/2mv^2
K = kinetic energy
m = mass
v = velocity
Bohr placed restrictions on the possible values of the angular momentum, predicting that the possible values for the angular momentum of an electron orbiting a hydrogen nucleus could be given by what formula?
L=nh/2pie
L = angular momentum of electron
n = principal quantum number
h = Planck’s constant
What is quantization and it’s relation to chemistry?
Quantization is the process of restricting continuous values to specific discrete values meaning certain properties of particles can only have distinct quantized values
This challenges classical continuous behavior, now a fundamental principal in quantum theory, revolutionizing our understanding of the atomic and subatomic world
What does “rh” in chemistry stand for?
Rydberg constant
equal to 2.18 x 10^-18 joules
Energy of an electron has what relationship with principal quantum number (n)?
They are directly proportional, as (n) increases, the energy of the electron also increases, thus the electron is found further from the nucleus
What is the principal quantum number (n)?
It represents the energy level or shell of an electron in an atom
The orbit with the smallest, lowest energy radius is defined as what?
The ground state (n=1)
When atoms are considered in a ground state it is in the state of lowest energy, in which all electrons are in the lowest possible orbitals
If an electron was promoted to an orbit with a larger radius (higher energy) the atom was said to be in…
An excited state
An atom is in this state when at least one electron has moved to a subshell of higher than normal energy
Electrons can be excited to higher energy level (excited state) how?
By heat or other energy forms to yield excited states
How long is the lifetime of an excited state?
It is brief, electrons will return rapidly to the ground state
When an electron goes from a excited state back to a ground state what results?
Emission of discrete amounts of energy in the form of photons
What is the formula for electromagnetic energy of photons?
(If frequency is not used)
E = hc/wavelength (lambda)
E = electromagnetic energy of photons
h = plancks constant
c = speed of light in a vacuum (3.00 x 10^8 m/s)
Combination of E = hf and
f = c/lambda
MNEMONIC
as electrons go from lower energy level to a higher energy level, they get AHED, what does AHED stand for?
A - absorb light
H - higher potential
E - excited
D - distant (from the nucleus)
Energy translations do not form a continuum but rather…
Are Quantized to certain values
What is the line spectrum?
The line spectrum is composed of light at specific frequencies, each line on the emission spectrum corresponds to a specific electron transition
Explain what the Lyman series, Balmer series, and Paschen series is?
These series’s are groups of hydrogen emission lines corresponding to transitions from energy levels:
N ≥ 2 to n = 1 -Lyman series
N ≥ 3 to n = 2 -Balmer series
N ≥ 4 to n = 3 -Paschen series
How are higher energy translations related to photon wavelengths
They are in opposition, higher energy translations equals shorter photon wavelengths
The energy of an emitted photon corresponds to the difference in energy between what?
The higher energy initial state and the lower energy final state
E_photon = E_initial - E_final
When an electron goes from a lower state to a higher state of energy then back to a lower state of energy, what is happening in these energy changes?
When electrons move from a lower state to a higher state of energy they undergo absorption and must absorb the right amount of energy to do so, they absorb this energy in the form of light, when electrons move from high back to low energy they undergo emission, emitting the same amount of energy in the form of light (photon)
What is the formula for energy of electron in atoms with only one electron, such as hydrogen?
E = -RH/n^2
E - energy of electron
RH - Rydburg constant
n - principal quantum number
Electrons move rapidly and are localized within regions of space around the nucleus called what
Orbitals
What is the Heisenberg uncertainty principal?
It’s impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron
What are the four quantum numbers
N, l, Ml, Ms
Any electron in an atom can be completely described by what?
It’s quantum numbers
What is the Pauli exclusion principal?
No two electrons in a given atom can posses the same set of four quantum numbers
Any position and energy of an electron described by its quantum numbers are known as it’s what?
Energy state
How does the values of the quantum numbers limit others?
The value of n limits the values of l, which limits the values of Ml
This is because it gets more localized as you go through the quantum numbers
Values of the quantum numbers qualitatively gives information about what?
Size, shape, and orientation of the orbitals
What is the first quantum number also known as?
The principal quantum number denoted as (n)
The larger (n) is the greater…
The energy, and radius of electrons shell
Maximum number of electrons in a shell is what formula
Max capacity of electrons in a shell = 2n^2
Energy difference is a function of
1/ni- 1/nf
ni = principal quantum number initial
nf = principal quantum number final
What does this mean as distance from nucleus increases?
Difference in energy between the 2 shells decreases as the distance from the nucleus increases
NEVER forget that electrons DO NOT travel in…
defined orbits
What is the second quantum number called
The azimuthal (angular momentum) quantum number
Denoted as “l”
The azimuthal quantum number represents what
Shape and number of sub shells within a given principal energy level
For any given value of n how do you find l?
l is 0 to (n-1)
Example: n=4 l = 0,1,2,3
N value also tells you the number of what within a shell?
Number of possible subshells
Example: n = 2 (l = 0,1) - 2 subshells
n = 4 (l = 0,1,2,3) - 4 subshells
What is spectroscopic notation?
The shorthand representation of the principal and azimuthal quantum numbers
n is given it’s same number
l follows the number in a letter corresponding to its value
What are the letters for “l” being
0,1,2, and 3
0 - s
1 - p
2 - d
3 - f
What is the max capacity of electrons within a subshell?
4l + 2
What happens to the energies of the subshells as l value increases
Energies of the subshells will increase, however the energies of subshells from different principal energy levels may overlap
Example: 4s subshell will have a lower energy level than 3d
What is the third quantum number?
The magnetic quantum number denoted as “ml”
What does the magnetic quantum number specify?
The particular orbit within a subshell where an electron is most likely to be found at a given moment in time
Each orbital can hold a max of how many electrons?
2
What are the possible values for ml?
The integers between -l and +l including 0
Example: l = 3 then ml has 7 orbitals (-3 to 3)
Shape of orbitals are dependent on what?
The subshell in which they are found
Orbitals in s subshell and p subshell are what shapes
s subshell - spherical
p subshell - dumbell shape
What are the 3 p orbitals often denoted as
px, py, pz
Shapes of orbitals are defined in terms of a concept called probability density, what does this mean?
Probability density refers to the likelihood that an electron will be found in a particular region of space
What is the fourth quantum number called?
The spin quantum number denoted as “ms”
An electron has how many spin orientations?
2, spin up (+1/2) and spin down (-1/2)
Whenever electrons are in the same orbital they must have what?
Opposite spins
Referred to as being paired in this case
Electrons in different orbitals with the same ms values are said to have…
Parallel spins
What is the electron configuration?
Representation of the arrangement of electrons in the atomic orbitals, following the order of filing based on energy levels and subshells
What notation does electron configuration use?
Spectroscopic notation
What does the superscript in electronic configuration represent
The number of electrons in the subshell
If the electron configuration is 2p^4 what does that imply about the energy levels before 2p?
They have already been filled (1s, 2s)
In what order do electrons fill their subshells?
According to the Aufbau Principal (building up principal) electrons will fill from lower-to higher-energy subshells
What is the n+l rule?
The lower the sum of the values of the first and second quantum numbers (n+l) the lower the energy of the shell
If 2 subshells posses the same n+l value what subshell fills first?
The lower n value has a lower energy level and will fill electrons first
What will fill first with electrons 5d vs 6s
6s because it has 6 n+l value while 5d has 7 n+l value
What is the lowest s subshell, p subshell, d subshell, and f subshell
s subshell - 1s
p subshell - 2p
d subshell - 3d
f subshell - 4f
What series is pulled out and placed below the rest of the periodic table in most tables?
The lanthanide and actinide series (f block)
In terms of spectroscopic notation on electronic configuration where is the lanthanide and actinide series placed between?
Lanthanide series is between 6s and 5d
Actinide series is between 7s and 6d
Electron configurations for elements can be abbreviated by placing what that precedes the element of interest in brackets?
The preceding noble gas
When dealing with an anion in electron configuration using noble gases what do you do?
You simply just add the needed amount of electrons
For the element “F” and “F-“ what is the electron configuration
F is [HE] 2s^2 2p^5
Then F- is [HE] 2s^2 2p^6
When dealing with cations in electronic configuration for elements what electrons do you remove first?
When dealing with a cation remove electrons from the subshells with the highest value for n first, if multiple subshells are tied for the highest n value, then electrons are removed from the subshell with the highest “l” value
Fe and Fe3+ electron configuration using noble gases
Fe is [Ar] 4s^2 3d^6
Then Fe+3 is [Ar] 3d^5
What does Hunds rule state?
That within a given subshell, orbitals are filled such that there are a maximum number of half filled orbitals with parellel spins
Electrons in the same orbital tend to be closer to each other and thus tend to…
Repel each other more than electrons placed in different orbits
Lower energies equals what referring to stability?
Higher stability
Half filled and fully filled orbitals tend to have what types of energy levels compared to other states
Lower energies
There are some exceptions to the Aufbau principal, why does this happen and what is it known as?
Instead of energy levels filling low to high they deviate to achieve a more stable configuration, known as the “half filled and fully filled subshell stability rule”
What are paramagnetic materials and how do they orient themselves?
Materials composed of atoms with unpaired electrons
This will orient their spins in alignment with a magnetic field, and thus the material will be weakly attracted to the magnetic field
What does paramagnetic cause in a magnetic field?
It will cause parallel spins in unpaired electrons and therefore cause an attraction (weak)
What are diamagnetic materials? How do they orient themselves in a magnetic field?
Materials consisting of atoms that have only paired electrons
will be slightly repelled by a magnetic field
In each row of periodic table how many elements are in the s-block,
d-block, and f-block
s-block - 2 elements
d-block - 10 elements
f-block - 14 elements
What are valence electrons?
Electrons of an atom that are in the outermost energy shell, most easily removed, and available for bonding
What subshell are the valence electrons in Elements in group 1 and 2
Only the highest s subshell
Group 13-18 has valence electrons in what subshell?
Highest s and p subshell
Transition elements are what groups?
Groups 3-12
Transition elements (groups 3-12) have valence electrons in what subshell?
Highest s and d subshells
Lanthanide and actinide series have valence electrons in what subshells?
Highest s and f subshells
