Atom Electron Structure

Electron Structure of Atoms

• These notes cover multiple-choice questions, matching exercises, and true/false questions about the electron structure of atoms, the periodic table, and electronic configurations.

Key Equations and Concepts

• E = h*f: E represents the energy of an electromagnetic radiation, and f represents the frequency of the radiation.
• In hydrogen atoms, electron transitions between energy levels involve the emission of radiation with specific frequencies.
• Moving from M to K emits frequency f1, M to L emits frequency f2, and L to K emits frequency f3 which are related by: f3 = f1 + f2.
• Higher frequency radiation corresponds to shorter wavelengths (λ).
• Going from M → K, M → L, and L → K results in radiations with frequencies f1, f2, f3 and wavelengths λ1, λ2, λ3.
• For frequencies: f2 < f1 < f3, and for wavelengths: λ2 > λ1 > λ3.
• Transitions from higher to lower energy levels give off radiation, such as from n=5 to n=2 emits higher frequency radiation.
• Heisenberg's Uncertainty Principle states it is impossible to simultaneously determine the exact position and momentum of a particle.
• Atomic orbital is a region in space where there is a high probability of finding an electron.
• There are three p orbitals in an energy level.
• The K and L shells contain one and four atomic orbitals, respectively.
• 2s and 3s atomic orbitals differ in size.
• 2s and 2p atomic orbitals have the same energy but differ in shape and spatial orientation.
• The azimuthal quantum number reveals the shape of the atomic orbital.

Orbitals and Subshells

• The 2p subshell has three atomic orbitals and can contain up to six electrons.
• The 3d subshell contains five atomic orbitals.
• Each atomic orbital can hold a maximum of two electrons.
• The combination of quantum numbers n=2, l=1, and m₁=0 describes one atomic orbital.
• 'Electron cloud' refers to the space where electrons may be found.
• In its ground state, hydrogen's single electron is in the 1s subshell because it has the lowest energy.
• The energy of 3s is greater than energy of 2p subshells.
• A 3d atomic orbital has lower energy than a 4p atomic orbital because the sum of n + l is smaller for 3d.
• The maximum number of electrons in each shell is determined by the Pauli Exclusion Principle.

Quantum Numbers and Atomic Structure

• The maximum number of electrons with quantum numbers n=3, l=2 is 10 electrons
• Maximum number of electrons with quantum numbers n=2, l=1, m₁=-1 is 2 electrons
• The maximum number of electrons with quantum numbers n=3, l=3 is 0
• Having two or more electrons with the same mₛ value in the same atomic orbital violates the Pauli Exclusion Principle.
• The electron configuration of Carbon's L shell (2s, 2px, 2py, 2pz) is 2s² 2px¹ 2py¹.
• For an atom with three electrons in the 2p subshell, the sum of the spin quantum numbers can be 3/2.
• If element Σ has three electrons in the 2p subshell when in the ground state, then its atomic number is seven.
• The smallest atomic number of an element with a total of 7 electrons in s orbitals in its ground state is 19.
• Oxygen has two orbitals containing only one electron in its ground state.
• Scandium's ground state electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s².
• Hund's rule: configurations (II) and (IV) for oxygen do not obey Hund's rule.
• Only configuration (IV) obeys the minimum energy principle for oxygen.
• Configurations (I), (II), and (III) do not obey the Pauli Exclusion Principle for oxygen.
• Electron configuration for the outer shell of phosphorus (Z=15) is shown in representation IV.
• Fluorine is in an excited state with the electronic configuration 1s² 2s¹ 2p⁶.
• The ions Mg²⁺ and F⁻ have electronic configurations (I) and (IV) respectively.
• The statement describing the impossibility of simultaneous determination of position and momentum of a particle expresses the Heisenberg uncertainty principle

Periodic Table

• An element is in the 3rd period if it has its outermost electrons in the M shell.
• Aluminum (Al, Z=13) is in the 3rd period and 13th group.
• An element belongs to the p-block if its highest energy electrons are in a p orbital.
• The element with electronic configuration [Ar] 3d¹⁰ 4s² 4p⁵ belongs to the 4th period and 17th group.
• Group IA (1) of the periodic table includes seven elements that feature ns¹ outer shell configurations.
• Scandium, ²¹Sc, has the lowest atomic number of the d-block elements.
• The s-block includes two groups with ns¹ or ns² outer electron configurations.
• Transition elements are located in the d-block of the periodic table, spanning seven periods and ten groups.
• Noble gases (ns² np⁶) belong to group 18 and there are six of them.
• K (Z=19), Ti (Z=22), Cu (Z=29) and As (Z=33), only Ti and Cu belong to the transition elements.
• Chemical bonds are formed because elements tend to transition to a more stable state with less energy.
• Fluorine, ₉F, has the smallest atomic radius among the options.
• Rubidium, ₃₇Rb, has the largest size among the options.
• Potassium, ¹⁹K has the smallest first ionization energy (E1).
• Oxygen, ₈O is the only element that is not electropositive.
• Caesium, ₅₅Cs, turns more easily into a cation.

Matching exercises

• Heisenberg: there is an impossibility in determining the location and the momentum of the electron
• De Broglie: Moving matter particles also act like waves
• Planck: electromagnetic radiation energy is quantized
• Bohr: electrons orbit the nucleus in circle shaped paths of specific radius
• The subshell L and M has possible quadruple values
• The quantum number column (II) corresponds to the items described in the "what it defines" list (III)
• The 3 items define the atomic orbitals
• ⅗ relates principal quantum number
• The 4th item defines the spin of the electron
• Link up the primary quantum number digit in column (II) with the number of atomic orbitals listed
• With the number of the underlays digit in column (II)
• Attach each layer or sublevel of column (II) to the maximum number of single electrons that can be contained in the column (I)
• And to the maximum number of electronic pairs that this may include