Chem Exam
Which of the following pairs of ions represent isoelectronic species? A) Na⁺ and N²⁻ B) Al³⁺ and O²⁻ C) K⁺ and Na⁺ D) Cl⁻ and F⁻ E) Al³⁺ and P³⁻
Al³⁺ and O²⁻ Isoelectronic species are elements/ions with the same electron configuration (and therefore the same number of electrons). Of the options given, the species Al³⁺ and O²⁻ both have the electron configuration of [Ne]1s²2s²2p⁶, meaning they are isoelectronic.
Which one of the following is the correct set of Lewis Symbols for CaCl₂? A) see problem image B) see problem image C) see problem image D) see problem image
B The calcium ion its two valence electrons to have a 2+ charge. The chlorine ions each gain an electron to fill their octets and have a -1 charge.
I₂ lewis dot structure
Both Is have 7 dots. Nonpolar covalent bond (shared) -- in between I--I
Which atom in the Br-F molecule has a partial positive charge (δ⁺)? A) Br B) F C) Both D) Neither
Br Partial charges are determined by the relative electronegativities of the atoms in a molecule; the less electronegative atom, which is Br, has a partial positive charge. In compound, + element first, - last.
Which atom in the Br-F molecule has a partial negative charge (δ⁻)? A) F B) Br C) Both D) Neither
F Partial charges are determined by the relative electronegativities of the atoms in a molecule; the more electronegative atom, which is F, has a partial negative charge. In compound, + element first, - last.
What element is designated by the orbital diagram below? A) N B) O C) F D) Ne E) Cl
F This orbital diagram contains a total of 9 electrons (1s²2s²2p⁵). Since the question is asking for an element and not an ion, the element must have the atomic number 9, meaning that this element must be F.
Which of the following bonds is a nonpolar covalent bond? A) H - F B) N - F C) F - Cl D) F - F
F - F In order to be nonpolar, the two atoms in the chemical bond need to have an electronegativity difference of 0.0-0.4.
All of the following pairs of ions are isoelectronic except which one? A) Al³⁺ and N³⁻ B) Fe²⁺ and Co³⁺ C) Fe²⁺ and Mn³⁺ D) K⁺ and Ca²⁺ E) Zn²⁺ and Cu⁺
Fe²⁺ and Mn³⁺ Of the options given, only the species Fe²⁺ (1s²2s²2p⁶3s²3p⁶3d⁶) and Mn³⁺ (1s²2s²2p⁶3s²3p⁶3d⁴) do not have the same electron configuration as they have different numbers of electrons, so they are not isoelectronic.
Which element has the electron configuration 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p²? A) Si B) Ge C) Sn D) Ga E) As
Ge This electron configuration ends with 4p, meaning it is an element in the p block (a main group element on the right-hand side of the periodic table) in the fourth row. The 2 in 4p² indicates that it is the second element in this row, so the element must be Ge
Which diatomic molecule has the largest dipole moment? A) HF B) HCl C) HBr D) HI
HF A dipole moment is a separation of charge within a molecule. A dipole moment occurs due to difference in electronegativity between the bonded atoms. Greater differences in electronegativity lead to a larger dipole moment. In this case, the differences in electronegativity values between hydrogen and fluorine is the greatest.
H₂S lewis dot structure
Hs- 1 dot S- 4 dots H-S-H polar covalent bonding
NH₃ lewis dot structure
Hs- no dots (bc its represented by bonds) N- 2 dots H-N-H H
A student draws the orbital diagram below for the 3d electrons in a V atom. What, if anything, is incorrect about the drawing? A) It violates the Aufbau principle. B) It violates the Pauli exclusion principle. C) It violates the Heisenberg uncertainty principle. D) It violates Hund's rule. E) There is nothing incorrect about the drawing
It violates Hund's rule. Hund's rule states that e-are added to the atomic orbitals with the same energy levels (degenerate orbitals) in such a way that each orbital is occupied by a single e-with the same spin (either +½ or -½) before any orbital can be occupied by 2e-. One of the orbitals has 2e- while 3 orbitals at equal energies contain 0e-, which is in violation of Hund's rule. According to Hund's rule, single e-, all with same spin, occupy orbitals before pairing of e- occurs.
Which of the following is an example of an ionic bond? A) K - F B) C - H C) Kr - H D) C - F
K - F K-F is an ionic bond because the difference in electronegativity is greater than 1.5 and it is between a metal and a nonmetal.
KCl lewis dot structure
K- 1 dot Cl- 7 dots Ionic bonding (electrons transferred)
What is the noble gas core in the electron configuration for Sb? A) Ne B) Ar C) Kr D) Xe E) Rn
Kr The noble gas core for a given element is the last noble gas filled in the periodic table prior to the given element. Here, the last noble gas prior to Sb is Kr, so that is its noble gas core.
Identify which of the following molecules has a double bond. A) O₂ B) H₂ C) Br₂ D) HF
Main group elements obey the octet rule. The Lewis structure for O₂ has a double bond with 4 valence electrons around each oxygen atom.
Consider the fourth period elements Ca, Mn, Co, Se, and Kr. Which of these atoms are paramagnetic? A) Ca, Mn, Co B) Mn, Co, Kr C) Ca, Kr, Se D) Mn, Co, Se E) Ca, Kr
Mn, Co, Se A paramagnetic element is one whose electron configuration contains any unpaired electrons, so they are those elements that are not at the right-hand edge of a given block (s, p, d, f) of the periodic table. Of these options, Kr and Ca are at the right-hand edges of the p and s block, respectively; the species Mn, Co, and Se are not at the edge of their blocks, and therefore have unpaired electrons and are paramagnetic.
Identify the region of the electromagnetic spectrum where the wavelength measurement of 630 nm can be found. A) Red B) Orange C) Yellow D) Green E) Blue
Orange The electromagnetic spectrum range for orange visible light is approximately 600 - 650 nm.
Which of the following states that no two electrons can have the same set of four quantum numbers? A) Hund's rule B) de Broglie wave equation C) Pauli exclusion principle D) Bohr equation E) Schrödinger equation
Pauli exclusion principle The Pauli exclusion principle states that no two electrons in a given atom can share the same set of four quantum numbers (nn, ℓℓ, mℓmℓ, msms).
What type of light on the electromagnetic spectrum has the lowest energy per photon? A) Radio waves B) Visible light C) All light has the same energy D) Microwaves E) Gamma waves
Radio waves Energy is directly related to frequency and inversely related to wavelength. Since radio waves have the lowest frequency and longest wavelength, they have the lowest energy.
Which element has the ground state electron configuration [Kr]5s²4d¹⁰5p³? A) Te B) Pb C) Sb D) Bi E) Sn
Sb- antimony This electron configuration ends with 5p, meaning it is an element in the p block (a main group element on the right-hand side of the periodic table) in the fifth row. The 3 in 5p³ indicates that it is the third element in this row, so the element must be Sb.
Y = fn(n, l, ml, ms)
Schrodinger Wave Equation
Which of the following atoms is diamagnetic? A) Mn B) O C) Sr D) Li E) Cl
Sr A diamagnetic ion/element is one whose electron configuration does not have any unpaired electrons. Of the options given, only Sr (electron configuration [Kr]5s²) has every electron paired with another electron, so it is diamagnetic.
Light wave A has a greater frequency than light wave B. Which has a greater wavelength? A) Wave A B) Wave B C) They're equal D) Not enough info
Wave B All light travels at the same speed (c), and since speed is equal to the product of wavelength and frequency, a higher frequency results in a shorter wavelength. Because wave A has a greater frequency than wave B, wave B must have the longer wavelength.
Which of the following is the electron configuration for Mn? A) [Kr]4s²3d⁵ B) [Ar]4s²3d⁵ C) [Ar]3d⁷ D) [Ar]4s²3d⁷ E) [Kr]3d⁵
[Ar]4s²3d⁵ The element Mn is a transition metal (meaning it is in the d block) and the fourth row; because elements in the d block have the quantum number n one less than their row in the periodic table, the electron configuration of Mn will end with 3d. The last noble gas filled prior to Mn is Ar, so the electron configuration of Mn is [Ar]4s²3d⁵.
polar (covalent) bond
a covalent bond with greater electron density around one of the two atoms
Which of the following has the shortest bond length? A) a single bond B) a double bond C) a triple bond
a triple bond Triple bonds are shorter than double bonds and double bonds are shorter than single bonds.
diamagnetic
all paired electrons
covalent bond
chemical bond in which two or more electrons are shared by two atoms
electromagnetic radiation
emission and transmission of energy in the form of electromagnetic waves
wavelength
horizontal distance between the crests or between the troughs of two adjacent waves
electron configuration
how the electrons are distributed among the various atomic orbitals in an atom
A single bond, compared to a double bond, A) is longer. B) is stronger. C) has a higher bond dissociation energy. D) is not capable of rotation.
is longer Single bonds are longer than double bonds.
Pauli exclusion principle
no two electrons in an atom can have the same four quantum numbers
frequency
number of complete wavelengths that pass a point in a given time
resonance structure
one of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure
photon
particle of light
Cation is always ________ than atom from which it is formed. Anion is always _______ than atom from which it is formed.
smaller; larger
electronegativity
the ability of an atom to attract toward itself the electrons in a chemical bond
formal charge
the difference between the number of valence electrons in an isolated atom and the number of electrons assigned to that atom in a Lewis dot structure
lattice energy
the energy required to completely separate one mole of a solid ionic compound into gaseous ions
bond energy
the enthalpy change required to break a particular bond in one mole of gaseous molecules
Hund's Rule
the most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins
Electron affinity
the negative of the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion
Effective nuclear charge (Zeff)
the positive charge felt by an electron
Aufbau Principle
the rule that electrons occupy the orbitals of lowest energy first
triple bond
two atoms share three pairs of electrons
double bond
two atoms share two pairs of electrons
paramagnetic
unpaired electrons
amplitude
vertical distance from the midline of a wave to the peak or trough
Based on the bond energies for the reaction below, what is the enthalpy of the reaction, in kJ? HC≡CH(g) + 5/2 O₂(g) → 2 CO₂(g) + H₂O(g)
-1222 kJ ΔHrxn = broken bonds - formed bonds Broken: 5/2 O-O, triple C-C, 2 C-H Formed: 4C=O, 2O-H [835 + 2(411) + 5/2(494)] - [4(799) + 2(459)] 2892 - 4114
The bond dissociation energy, in kJ, to break 4 bond(s) in 1 mole of CH₄ molecules is
1,644kJ 4 bonds x 411 kJ/mol each
What is the electron configuration of K⁺? A) 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶ B) 1s²2s²2p⁶3s²3p⁶ C) 1s²2s²2p⁶3s²3p⁶4s² D) 1s²2s²2p⁶ E) 1s²2s²2p⁶3s²3p⁵
1s²2s²2p⁶3s²3p⁶ The element K is in the first column of the periodic table (meaning it is in the s block) and the fourth row, so its electron configuration will end with 4s¹. The electron configuration of K is 1s²2s²2p⁶3s²3p⁶4s¹. However, the K⁺ ion has one fewer electron (due to its positive charge), so the highest-energy electron must be removed from K to create K⁺, meaning its electron configuration will be 1s²2s²2p⁶3s²3p⁶.
The ground state electron configuration of a Se atom is A) 1s²2s²2p⁶3s²3p⁶4s²4p⁴ B) 1s²2s²2p⁶3s²3p⁶4s²4d¹⁰4p⁴ C) 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴ D) 1s²2s²2p⁶3s²3p⁴ E) 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p³
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴ The element Se is a main-group element on the right-hand side of the periodic table (meaning it is in the p block) and the fourth row, so its electron configuration will end with 4p. The electron configuration of Se1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴
Which of the following electron configurations represent a transition metal atom? A) 1s²2s²2p⁶ B) 1s²2s²2p⁶3s²3p⁴ C) 1s²2s²2p⁶3s²3p⁶4s² D) 1s²2s²2p⁶3s²3p⁶4s²3d⁷ E) 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p¹
1s²2s²2p⁶3s²3p⁶4s²3d⁷ The transition metals are in the d block of the periodic table, meaning their electron configurations will end with a partially or completely filled d orbital. Of these options, only 1s²2s²2p⁶3s²3p⁶4s²3d⁷ (Co) meets this criteria.
What is the energy (in J) of a photon with a frequency of 7.01 × 10¹⁴ s⁻¹? (h = 6.626 × 10⁻³⁴ J • s)
4.64E-19 E = h x v E = 6.626E-34 x 7.01E14
Of the following, which sublevel is filled last? A) 3d B) 4s C) 4p D) 4d E) 5s
4d According to the Aufbau principle, the order in which atomic orbitals are filled is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, ... Of the options given, the 4d orbital is at the highest energy, and therefore it will be filled with electrons last.
Which of the orbital electron configurations is not possible? A) 2s¹ B) 3d¹⁰ C) 4p⁷ D) 4f⁷ E) 2p⁶
4p⁷ The number of atomic orbitals with a given value of n is determined by the quantum number, ℓ. ℓ = 1 represents the set of p orbitals, which consists of three orbitals which can each hold two electrons, meaning that a p orbital can only hold 6 electrons. Therefore, the electron configuration 4p⁷ is not possible.
How many electrons are shared between two atoms in a triple bond? A) 2 B) 3 C) 4 D) 6
6 Two electrons are shared between two atoms in an individual bond, therefore in a triple bond 2 × 3 = 6 electrons are shared.
