General Chemistry- Atomic Structure Flashcards
What are the three subatomic particles?
Protons
Neutrons
Electrons
What is the fundamental unit of charge?
+1e
e=1.6x10^-19C
What’s the mass of a proton?
1 Atomic Mass Unit (amu)
What is the atomic number?
(Z) or the number of protons found in an atom, of that element.
What charge do neutrons have?
None, they are neutral
What makes up almost the entire mass of an atom?
Sum of the protons and neutrons in the nucleus
What is an isotope?
Atoms that share an atomic number, but have different mass numbers
What is the charge of an electron?
-1e
e=1.6x10^-19C
What is the mass of an electron?
1/2000 of a proton
What occurs due to the small masses of protons and electrons?
The electrostatic force of attraction is far greater than the gravitational force of attraction
Varying distance from the nucleus, causes what?
Varying levels of electrical potential energy.
Which have higher energy, electrons closer to the nucleus or further from the nucleus?
Further from the nucleus
What are the valence electrons?
Electrons furthest from the nucleus because they have the strongest interactions with the surrounding environment and weakest interactions with the nucleus
Valence electrons are much more likely to be involved in what?
Bonds with other atoms
Why are valence electrons more likely to bond with other atoms?
They experience the least electrostatic pull from their own nucleus
What do valence electrons determine?
The reactivity of an atom
What does the transferring of valence electrons allow?
Elements to fill their highest level to increase stability
What is the name of a positively charged atom?
Cation
What is the name of a negatively charged atom?
Anion
What are the symbols of protons, neutrons and electrons?
Protons: p, p+, 1/1H
Neutron: N^0, 1/0n
Electron: e-, or 0/-1e
See table 1.1
Where are electrons found?
Orbitals
Which subatomic particle is the most important for determining each of the following properties:
Charge:
Atomic Number:
Isotopes:
Charge: Electrons
Atomic Number: Protons
Isotopes: Neutrons
What’s the difference between atomic mass and mass #?
Nothing, they are synonymous
What is the difference between atomic weight and atomic mass?
Atomic weight is constant for a given element, while mass changes from isotope to isotope
What is the definition of atomic mass unit?
1/12 mass of the carbon-12 atom about 1.66x10^-24g.
AMU=Mass of proton or neutron
Where might mass be loss in regards to the mass number?
Binding energy
What is the greek meaning of isotopes?
Same place
How do you refer to an isotope?
The element name followed by the mass number.
Ex: carbon-12
What are the three isotopes of hydrogen?
Protium (greek: first) 1 proton + 1AMU
Deuterium (second) 1 proton, 1 neutron, 2AMU
Tritium (third) 1 proton, 2 neutrons, 3 amu
In nature almost all elements exist as what?
Two or more isotopes
What is the atomic weight?
The weighted average of all the naturally occuring isotopes of an element.
What do half-lives correspond with?
Stability
What do half-lives help determine?
The relative proportions of the different isotopes in nature.
What is a mole?
A number of “things” based on Avogadro’s number
What is avogadro’s number?
NA= 6.02x10^23
What are the definitions of atomic mass and atomic weight?
Atomic mass: Just slightly less than the sum of the masses of protons and neutrons in a given atom of an elements
Atomic weight: Average weight of the naturally occuring isotopes
While molar mass is typically written in grams per mole (g/mol), is the ratio moles per gram (mol/g) also acceptable?
The ratio is equivalent concept. It is therefore acceptable, as long as units can be cancelled in dimensional analysis.
What did Ernest Rutherford give evidence to? What date?
Evidence that an atom has a dense positively charged nucleus, which is only a small portion of the volume in 1910
What did Max Planck develop? What year?
1899-Quantum theory
What is quantum theory?
Energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta.
How is the energy of a quantum determined?
The Planck relation: E=hf
What do the letters represent in the Planck relation?
E=hf
E is energy
h is proportionality constant known as Planck’s constant= 6.626x10^-34Js
F or v=Frequency of radiation
What is angular momentum?
L=mvr
What is kinetic energy?
K=1/2mv^2
What did Bohr determine that went against the common knowledge of classical mechanics?
Bohr placed restrictions on the possible values of the angular momentum, when classical mechanics postulates that an object revolving around a circle has an infinite number of values
What did Bohr develop?
A model of the electronic structure of a hydrogen atom and an equation that could predict the values for angular moment of an electron orbiting a hydrogen nucleus.
What was Bohr’s equation for angular moment of an electron?
L=nh/2(pi)
What do the letters represent in Bohr’s equation for angular momentum of an electron?
L=nh/2(pi)
n: the principal quantum number
h: Planck’s constant
When was Bohr’s discovery?
1913
What did Bohr postulat?
The centripetal force acting on the electron as it revolved around the nucelus was created by the elecctrostatic force between the positively charged proton and the negatively charged electron
What is the equation for Bohr’s use of angular momentum to find the energy of an electron?
E=-(Rh)/n^2
What do the letters mean in the equation for Bohr’s equations to find the energy of an electron?
E=-(Rh)/n^2
(Rh): Rydberg unit of energy= 2.18x10^-18J/electron
n: principal quantum number
Does the energy of an electron increase or decrease the further it is from the nucleus?
Energy of an electron increases the farther out from the nucleus that it is located
Does the electron always have an attractive force towards a proton?
Yes, an electron in any of its quantized states in the atom will have an attractive force towards the proton
How does energy of an electron change?
In discrete amounts with respect to the quantum number.
How does angular moment of an electron change?
Only in discrete amounts with respect to the principal quantum number
What is an important point when looking at the energy of an electron?
While the magnitude of the fraction is getting smaller, the actual value it represents is getting larger (becoming less negative.)
How does Bohr describe the hydrogen atom?
The structure of the hydrogen atom as a nucleus with one proton forming a dense core, around which a single electron revolved in a defined pathway (orbit) at discrete energy value
According to Bohr’s theory, what could result in an electron jumping?
Transfer of the exact amount of energy equal to the difference between one orbit and another
What is ground state?
The orbit with the smallest, lowest-energy radius (n=1)
What is an excited state, in regards to an electron?
At least one electron has moved to a subshell of higher than normal energy
What do we know now, that contradicts Bohr’s model?
Electrons are not restricted to specific pathways, but tend to be localized in certain regions of space.
As electrons go from a lower energy level to a higher energy level they get what?
Aborption of light Higher potential Excited Distant (from the nucleus) (AHED)
How can electrons be excited to a higher energy level?
Heat
Other energy forms
Once the electrons are no longer being excited, what occurs?
Electrons will rapidly return to ground state
What is a result of electrons returning to ground state?
Emission of discrete amounts of energy in the form of photons
What equation demonstrates photon emission?
E=hf (a photon is emitted with energy)
What is the equation for electromagnetic energy of a photon?
E= hc/(/) (p.12)
What do the letters represent in the equation for electromagnetic energy of a photon?
E= hc/(/)
h: Planck’s constant
c: speed of light in a vacuum (3.00X10^8m/s)
(/): wavelength of the radiation
What is the speed of light in a vacuum?
3.00x10^8m/s
What happens when an electron returns to ground state?
Electrons will each emit a photon with a wavelength characteristic of the specific energy transition it undergoes.
Do energy transitions of electron form a continum?
No, they are quantized to certain values
What is a line spectrum?
Lines which corresponds to specific electron transition
Each element has a unique what?
Atomic emission spectrum which can be used as a fingerprint for the element
How can elements be determined on other planets/stars?
The light from a star can be resolved into its component wavelengths which then match to the known line spectra of the elements
What is the Lyman series?
The group of hydrogen emission lines corresponding to transitions from energy n>2 to n=1
Which element does the Bohr model explain in regards to the emission spectrum?
The atomic emission spectrum of hydrogen
What is the Balmer series?
The corresponding transitions from energy levels n>3 to n=2
What is the Paschen series?
Transitions from n>4 to n=3
Which has larger energy transitions, Lyman or Balmer series?
Lyman series compared to Balmer series
Which series has wavelengths in the visible region?
Balmer series with four wavelengths in the visible region
Which series has shorter photon wavelengths in the UV region?
Lyman series
Energy is inversely proportional to what?
wavelength
What is the equation for energy and wavelength?
E=hf=hc/(/)
What is the combined equation of Bohr and Planck’s calculations?
E=hc/(/)=-R [(1/(ni)^2)-(1/(nf)^2]
What is the equation explaining that combines Bohr’s and Planck’s calculations?
The energy of the emitted photon corresponds to the difference in energy between the higher-energy initial state and the lower-energy final state.
What occurs when an electron is excited and is moving to a higher energy level?
It must absorb exactly the right amount of energy to make that transition. Electron transition results in energy absorption at specific wavelengths
What are the two spectrums given off by an electron?
Emission spectrum
absorption spectrum.
What can the two spectrums show?
Unique elements and which element is present in a given area. Absorption and emission wavelengths of an element are what? The exact same
Why are absorption and emission wavelengths the same?
The difference in energy between levels remains unchanged so emission and absorption will be the same.
What is required to identify elements in the gas phase?
Absorption spectra
Each element has what in regards to identification spectras?
Each element has a characteristic set of energy levels.
What was the flaw of Bohr’s model?
Inadequate to explain the structure and behavior of atoms containing more than one electron
What didn’t Bohr’s model take into account?
The repulsion between multiple electrons surround the nucleus
What is the important difference between Bohr’s model and the modern quantum model?
Bohr postulated that electrons follow a clearly defined circular pathway or orbit at a fixed distance from the nucleus, wherreas modern quantum mechanics has shown that this is not the case.
What are orbitals?
Localized regions of space around the nucleus where electrons move rapidly
Orbitals are part of which atomic model?
Quantum Mechanical Model of Atoms
What is impossible to pinpoint int he modern quantum model?
Exact whereabouts of an electron at a given moment in time
What is the best that can be done to determine the location of an electron in the quantum mechanical model?
Describe the probability of finding an electron within a given region
What is the Heisenberg Uncertainty Principle?
It is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron
What are the four quantum number that can describe an atom?
n, l, (ml), (ms)
What is the Pauli exclusion principle?
No two electrons in a given atom can possess the same set of four quantum numbers.
What is an electron’s energy state?
The position and energy of an electron described by its quantum numbers
What does the values of n limit?
The value of n limits the values of l, which limits the values of (ml)
What do the values of the quantum numbers five info about?
Size
Shape
Orientation of the orbitals
What is the pricipal quantum number?
First quantum number, denoted by the letter “n.”
What quantum number is used in Bohr’s model?
First quantum number which takes on any positive integer value
What is the meaning of principal quantum number n?
The larger the integer value of n, the higher the energy level and radius of the electron’s shell.
Each shell has the capacity to what?
hold a certain number of electrons
What is the equation for the maximum number of electrons within a shell?
2n^2
What is the 2nd quantum number?
Azimuthal quantum number (angular momentum) designated by the letter “l”
What does the second quantum number refer to?
The shape and number of subshells within a given principal energy level (shell).
What is important about the 2nd quantum number?
It has important implications for chemical bonding and bond angles
What is the equation to determine the range of possible values for ‘l”?
l=(n-1)
Wjat os spectroscopic notation?
The shorthand representation of the principal and azimuthal quantum number.
What letters are designated by which subshells?
l=0 subshell: s
l=1 subshell: p
l=2 subshell: d
l=3 subshell: f
Looking at the periodic table, which groups are in which subshells?
Alkali: s-block plus helium
Halogen: p-block
transition: d block
Lanthanide/Acinide: f-block
What is the equation for the maximum number of electrons within a subshell?
4”l”+2
What increases with “l” value?
Energies of the subshell
What is the third quantum number?
Magnetic quatnum number desginated by the letter (ml)
What does the third quantum number specify?
The particular orbital within a shubshell where an electron is mostlikely to be found at a given moment in time.
Each given orbital can hold a max of how many electrons?
Two electrons
What are are the possible values of (ml)?
The possible values are the integers between -1 and +1 including 0
The four different orbitals have how many orbitals each?
s subshell: 1 (0)
p subshell: 3 (-1, 0, +1)
d subshell: 5 (-2, -1, 0, 1, 2)
f subshell: 7 (-3, -2, -1, 0, 1, 2, 3)
The shape of the orbitals is dependent of what?
Dependent on the subshell
What shape is the s subshell?
Spherical
What shape is the p subshell?
Dumbell shaped
How is the p subshell orbitals aligned?
Along the x, y, and z axes
What are the p subshell orbitals referred to as?
px, py, pz
How are the d and f subshells shapes defined?
By the concept probability density
How many elements are contained in each subshell block on the periodic table?
s block: 2 groups of elements
p block: 6 groups of elements
d block: 10 groups of elements
f block: 14 groups of elements
What is the 4th quantum number?
Spin quantum number or (ms)
How many spin orientations does an electron have?
Two spin orientations
+1/2) and (-1/2
When two electrons are in the same orbital, what happens?
They must have opposite spins
What are electrons refered to as when they are in the same orbital?
Paired
What does electrons having parallel spins mean?
Electrons in different orbitals with the same (ms) values have parallel spins
What is electron onfiguration?
The pattern by which subshells are filled and the number eletrons within each principal energy level and subshell
How do you read spectroscopic notation?
The first number denotes the principal energy level, the letter designates the subshell and the superscript give the number of electrons in that subshell.
What is the electron subshell flow diagram?
See figure 1.12 page 20. The tree
What is the Aufbau Principle?
Electrons fill from lower to higher energy subshells. Each subshell will fill completely before electrons begin to enter the next one
What is the building-up principle?
The Aufbau principle
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 subshell
For the n+l rule, what do you do if two subshells has the same n+l value?
The subshell with the lower n values has a lower energy.
What are the two ways to not memerize the subshell flow?
The n+l rule
Reading the periodic table
How can electron configuration be abbreviated?
By placing the noble gas that precedes the element in brackets
How do you write the electron configuration for Anions?
Because Anions have additionally charged electrons you fill them up the same way as above.
How do you write electron configuration for Cations?
Start with the neutral atom, and remove electrons from the subshells with the highest value for n first.
What happens if multiple subhsells are tied for highest n vlaue when removing electrons from Cations?
Electrons are removed from the subshell with the highest l value
What is Hund’s rule?
Within a given subhsell, orbitals are filled such that there are a maximum number of half-filled orbitals with parallel spins.
When do electrons fill according to Hund’s rule?
When subhsells contain more than one orbital, the orbitals will fill according to Hund’s rule.
What is the basis for Hund’s rule?
Electron repulsion: electrons in the same orbital tend to be closer to each other and thus repel each other more than electrons placed in different orbitals.
Which orbitals have lower energies?
Half-filled and Fully filled
What does lower energies in an orbital mean?
Higher stability
What groups are the notable exceptions to electron configuration?
Chromium and Copper groups
What is the exception for Chromium and copper in regards to its configuration?
Instead of filling up the s subshell it fills up a larger subshell first because the electrons can fill up half or full in that other subshell.
Can similar exceptions to the configuration of electrons be seen in the f subshell?
Yes
Can similar exceptions to the configuration of electrons be seen in the p subshell?
Never! the extra stability doesn’t outweight the cost
What is affected by the presence of paired or unpaired electrons?
The chemical and magnetic properties of an atom or molecule.
What materials are paramagnetic?
Atoms with unpaired electrons will orient their spins in alignment with a magnetic field and be weakly attracted to the magnetic field.
What causes materials to be diagmagnetic?
Materials consistinng of atoms that have only paired electrons will be slightly repelled by a magnetic field.
What are the valence electrons?
Electrons that are in its outermost energy shell
Are most easily removed
Are available for bonding
What are the the characteristics of valence electrons?
Are most easily removed
Are available for bonding
Dominate chemical behavior
For groups IA and IIA (1 and 2), which subshells have valence electrons?
The highest s subshell electrons are valence electrons
For group IIIA-VIIIA (13-18), which subshells have valence electrons?
The highest s and p subshells electronns are valence electrons
For transition elements, which subshells have valence electrons?
Highest s and d subshell electrons
For lanthanide and actinide series elements, which subshells have valence electrons?
Highest s and f subhsells
Which period of elements violates the octet rule?
Elements in period three (starting with sodium) and below may accept electrons into their d subshell which allows them to hold more than eight electrons in their valence shell.
