Final Chem 1A

Which atom in the Br-F molecule has a partial positive charge (δ⁺)? A) Br B) F C) Both D) Neither

A) Br. Partial charges are determined by the relative electronegativities of the atoms in a molecule; the less electronegative atom, which is BrBr, has a partial positive charge.

Which atom in the C-F bond has a partial positive charge (δ⁺)? A) C B) F C) Both D) Neither

A) C. Partial charges are determined by the relative electronegativities of the atoms in a bond; the less electronegative atom, which is CC, has a partial positive charge.

Based on the orbital filling configurations, predict which of the following species would have the strongest bond. A) C₂²⁻ B) C₂⁻ C) C₂

A) C₂²⁻

Which atom in the Br-F molecule has a partial negative charge (δ⁻)? A) F B) Br C) Both D) Neither

A) F. Partial charges are determined by the relative electronegativities of the atoms in a molecule; the more electronegative atom, which is FF, has a partial negative charge.

Which diatomic molecule has the largest dipole moment? A) HF B) HCl C) HBr D) HI

A) 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. Therefore, HFHF will have the largest dipole moment.

Adding electrons to bonding molecular orbitals will: A) Increase the bond order B) Decrease the bond order C) Have no effect on the bond order D) Weaken the bond

A) Increase the bond order

Which of the following is an example of an ionic bond? A) K - F B) C - H C) Kr - H D) C - F

A) 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.

Which one of the following is the least electronegative atom? A) Na B) Cl C) P D) Al

A) Na. Alkali metals and alkaline earth metals have lower electronegativities.

Identify which of the following molecules has a double bond. A) O₂ B) H₂ C) Br₂ D) HF

A) O₂. Main group elements obey the octet rule. The Lewis structure for O2O2 has a double bond with 4 valence electrons around each oxygen atom.

Which one of the following trends appears when considering lattice formation enthalpies (lattice energies)? A) The higher the charge on the ions, the higher the lattice formation enthalpy. B) The more ions present in an ionic compound, the smaller the lattice formation enthalpy. C) The larger the internuclear distance between ions in an ionic compound, the higher the lattice formation enthalpy. D) In general, alkali metals have larger lattice formation enthalpies than alkaline earth metals with the same anions.

A) The higher the charge on the ions, the higher the lattice formation enthalpy. Consider the charge on the ions. The higher the charges, the higher the lattice formation enthalpy (lattice energy).

Which set of hybrid orbitals is represented by the picture below? A) sp B) sp² C) sp³ D) dsp³ E) d²sp³

A) sp

A molecule that contains delocalized electrons ________ A) will have at least two resonance structures. B) will have only single bonds in its chemical structure. C) will be any molecule that contains a double bond. D) will be any molecule that contains a π bond.

A) will have at least two resonance structures.

The best reason for why a covalent bond forms is

Atoms with high electronegativities will not lose electrons, so instead they share electrons to reach a stable number of valence electrons. Covalent bonds form because atoms with high electronegativities will not lose electrons, so instead they share electrons to reach a stable number of valence electrons.

Which atomic orbitals from carbon hybridize to form the bonds in CH₄? A) 1s, 2p_x, 2p_y, 2p_z B) 2s, 2p_x, 2p_y, 2p_z C) 3s, 3p_x, 2p_y, 2p_z D) 2s, 2p_x, 2p_y

B) 2s, 2p_x, 2p_y, 2p_z. Draw the orbital energy diagram for C to find where its valence electrons are. They are found in 2s,2pₓ,2py,2pz2�,2�ₓ,2��,2��.

Which atom in the P-Cl bond has a partial negative charge (δ⁻)? A) P B) Cl C) Both D) Neither

B) Cl - Partial charges are determined by the relative electronegativities of the atoms in a bond; the more electronegative atom, which is ClCl, has a partial negative charge.

Which hybrid orbitals overlap in the C - O bond in CF₂O? A) Csp² - Os B) Csp² - Osp² C) Csp² - Osp³ D) Csp³ - Osp³ E) Csp³ - Osp

B) Csp² - Osp². In the Lewis structure of CF2OCF2O both the C and O atoms are sp2sp2 hybridized. The C-O sigma bond is formed between the C−sp2C−sp2 orbital and the O−sp2O−sp2 orbital.

Which one of the following statements best describes electronegativity in atoms? A) Electronegativity is what happens when an atom gains an electron to become an anion. B) Electronegativity is the attraction an element's nucleus has for the electrons in a chemical bond. C) Electronegativity is the energy lost when an atom gains an electron. D) Electronegativity is the energy absorbed when an atom loses an electron.

B) Electronegativity is the attraction an element's nucleus has for the electrons in a chemical bond.

A non-zero bond order indicates the ability of a molecule to be stabilized by a bonding interaction. Using MO filling diagrams, determine which of these diatomic species would have a bond order > ½. A) Be₂ B) Li₂ C) F₂⁻ D) Ca₂ E) B₂⁺

B) Li₂

Which of the following is not an example of a covalent bond? A) N - N B) Mg - N C) N - O D) H - H

B) Mg - N. Typically a nonmetal bonded to a nonmetal is a covalent bond.

Which of the following molecules is paramagnetic? A) N₂ B) O₂ C) H₂ D) F₂ E) Cl₂

B) O₂.

Which one of the following statements is FALSE? A) An sp orbital is made from combining an s and one p orbital B) Pi bonds are formed from the overlap of hybrid orbitals C) Atoms which have sp³d hybridization must be in the third period of the Periodic table or below D) The combination of an s and three p orbitals results in the formation of four sp³ orbitals with angles of 109.5º E) The type of hybrid orbitals on an atom are determined by the number of electron domains needed to form the molecule

B) Pi bonds are formed from the overlap of hybrid orbitals. This is false because pi (π�) bonds are formed from the overlap of p orbitals.

What is the hybridization of all the carbon atoms in benzene (C₆H₆)? A) sp B) sp² C) sp³ D) dsp³ E) d²sp³

B) sp².

Consider the MO diagrams for these diatomic species. Rank the following diatomic species in order of bond dissociation energy (from smallest to largest).

BN⁺ < BN < BN⁻

Based on their positions in the periodic table, which of the following bonds is the most polar? A) O - F B) C - F C) B - F D) F - F

C) B - F. Polar bonds occur between two nonmetals and have a difference in electronegativities of the atoms.The further apart two atoms are in the same period, the greater the polarity of the bond.

Which hydrocarbon has all of its atoms in the same plane? A) C₂H₆ B) CH₄ C) C₂H₄ D) C₃H₄

C) C₂H₄. C2H4 is a planar molecule with both carbon atoms being sp2sp2 hybridized with a trigonal planar electron geometry.

Which of the following is an example of a covalent bond? A) K - Cl B) Al - Cl C) H - Cl D) Al - Al

C) H - Cl. Covalent bonds are typically formed between two nonmetals.

Which of the following bonds is a polar covalent bond? A) Li - Cl B) Cl - Cl C) H - Cl D) Li - Li

C) H - Cl. Polar bonds occur between two nonmetals and have a difference in electronegativities of the atoms of approximately 0.5-2.0.

Which hydrocarbons shown below has all of its atoms in the same plane? A) I B) II C) III D) IV E) V

C) III. Structure III is a planar molecule with both carbon atoms being sp2sp2 hybridized with a trigonal planar electron geometry.

Which of the following is an example of an ionic bond? A) F - F B) O - F C) Na - O D) Na - Na

C) Na-O. is an ionic bond because the difference in electronegativity is greater than 1.5 and it is between a metal and a nonmetal.

Which one of the following statements is FALSE? A) The bond between carbon and oxygen in CO is shorter than the bond between carbon and oxygen in CO₂ B) Nitrogen, in its elemental form, has a triple bond between the two atoms C) The bond between the carbons in the molecule H₂C=CH₂ is stronger than the bond between the carbons in HC≡CH D) A single bond consists of two electrons being shared

C) The bond between the carbons in the molecule H₂C=CH₂ is stronger than the bond between the carbons in HC≡CH. - A carbon-carbon triple bond is stronger than a carbon-carbon double bond.

Which group in the periodic table tends to have high electronegativity values?

C) The halogens. The halogens tend to have the highest electronegativity values in the periodic table.

The term 'delocalization' refers to A) electrons being shared between two atoms in σ bonds. B) electrons being shared between two atoms in π bonds. C) electrons being shared via π bonds between more than just two atoms. D) electrons being shared via σ bonds between more than two atoms. E) the uncertainty of the exact location of an electron occupying an orbital.

C) electrons being shared via π bonds between more than just two atoms.

Which one of the following bonds has the least ionic character? A) Li - Cl B) Na - Cl C) Ca - Cl D) B - Cl

D) B - Cl. A bond between B-Cl would have the least ionic character because it is between two nonmetals.

Based on their positions in the periodic table, which of the following bonds is the most polar? A) C - O B) C - N C) C - B D) C - F

D) C - F. Polar bonds occur between two nonmetals and have a difference in electronegativities of the atoms. The further apart two atoms are in the same period, the greater the polarity of the bond.

Which molecule contains sp hybridized orbitals? A) C₂H₆ B) CH₄ C) C₂H₄ D) C₃H₄

D) C₃H₄. In the Lewis structure of C3H4C3H4, the central carbon atom is sp-hybridized.

Which of the following bonds is a nonpolar covalent bond? A) H - F B) N - F C) F - Cl D) F - F

D) 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.

Which one of the following is the most electronegative atom? A) C B) N C) O D) F

D) F. Fluorine is the most electronegative element.

The molecular formulas for the halogens are Br₂, Cl₂, F₂, and I₂. Which has the longest bond length and why? A) F₂ is longest because fluorine is the most electronegative halogen. B) I₂ is longest because the bond is formed from electrons in the 4p orbital, which has the largest radius. C) Br₂ is longest because its 3d electrons become involved in the bonding. D) I₂ is longest because the bond is formed from electrons in the 5p orbital, which has the largest radius. E) Cl₂ is longest because chlorine has the largest atomic radius.

D) I₂ is longest because the bond is formed from electrons in the 5p orbital, which has the largest radius. - Bond length is dependant on the atomic radius which depends on the size of the atomic orbitals forming the bond. Iodine bonds are formed from 5p orbitals which have the largest size of the bonding orbitals in these four halogens.

Determine which of the following species would have the lowest ionization energy. A) N₂⁺ B) N₂ C) N₂⁻ D) N₂²⁻

D) N₂²⁻

Where are the π electrons delocalized in a benzene (C₆H₆) molecule? A) They are delocalized between the carbons in the plane of the ring. B) They are delocalized between the carbons and above the plane of the ring. C) They are delocalized between the carbons and below the plane of the ring. D) They are delocalized above and below the plane of the ring.

D) They are delocalized above and below the plane of the ring.

A π bond could be formed from the overlap of which two orbitals? A) two sp² hybrid orbitals B) a 1s and a sp² hybrid orbital C) a sp and a sp² hybrid orbitals D) two unhybridized p orbitals

D) two unhybridized p orbitals

hich diatomic molecule has the smallest (lowest) dipole moment? A) F₂ B) O₂ C) N₂ D) H₂ E) All equal

E) All equal - Homonuclear molecules do not have charge separation between the identical nuclei and therefore contain no dipole moments.

Which one of the following statements is FALSE? A) In a polar covalent bond, the electrons in the bond will be closer to the more electronegative atom B) In a nonpolar covalent bond, the electrons in the bond are equally balanced between the two atoms C) In a bond between boron and hydrogen, the electrons will be unequally shared D) A bond between nitrogen and oxygen will be polar E) In a bond between magnesium and sulfur, the electrons will be shared and closer to the sulfur

E) In a bond between magnesium and sulfur, the electrons will be shared and closer to the sulfur. - Magnesium is a metal and sulfur is a nonmetal. These would form an ionic bond and not a covalent bond.

Which one of the following statements is FALSE? A) Ionic bonding results from the transfer of electrons from one atom to another B) Dipole moments result from the unequal distribution of electrons in a molecule C) The electrons in a polar bond are found nearer to the more electronegative element D) A molecule with very polar bonds can be nonpolar E) Linear molecules cannot have a net dipole moment

E) Linear molecules cannot have a net dipole moment. - Linear molecules can easily be polar given the appropriate arrangement of elements. Draw the Lewis structure for HCNHCN for an example.

A bond order of zero indicates that a species is unstable. Using MO diagrams, determine which of these diatomic species would have a bond order of zero. A) B₂ B) Mg₂⁺ C) F₂ D) He₂⁺ E) Mg₂

E) Mg₂

Based on the orbital filling configurations, determine which of the following species would have the greatest bond order upon addition of an electron. A) O₂ B) O₂⁺ C) O₂²⁺ D) N₂ E) N₂⁺

E) N₂⁺

A single bond, compared to a double bond,

Is longer. - Single bonds are longer than double bonds.

Consider the MO diagram below for these diatomic species. Rank the following diatomic molecules in order of bond length (from smallest to largest).

NO⁺ < NO < NO⁻

In a polar covalent bond,

One atom in the bond must have higher electronegativity than the other atom. - Polar bonds occur between two nonmetals and have a difference in electronegativities of the atoms.

A lattice dissociation enthalpy (lattice energy) is

The amount of energy that must be supplied to break an ionic solid into its individual gaseous ions.

The reason an ionic bond forms can best be described as

The energy change for electron transfer results in a large gain in stability when the ionic bond forms.

A bond dissociation energy is

The energy required to break a covalent bond into two fragments each with one electron from the bond. - A bond dissociation energy is the energy required to break a covalent bond into two fragments each with one electron from the original bond.

In a covalent bond

Two atoms share valence electrons and those shared electrons form the chemical bond. In a covalent bond, two atoms share valence electrons and those shared electrons form the chemical bond.

Single, double, or triple covalent bonds in a carbon atom are formed from

Valence electrons.

A more electronegative atom

Will have more attraction to the electrons in a chemical bond.

Complete the MO diagram (below) to determine if BN is paramagnetic or diamagnetic.

diamagnetic.

What is the shape of the 2p orbitals?

dumbbell. 2p orbitals have a dumbbell shape.

What would be the bond order of the hypothetical molecule Ar₂?

0

Use the blank MO diagram (below) to aid in answering the question. Calculate the bond order for I₂.

1

In sp²-hybridized orbitals, how many p-orbitals remain to form multiple bonds?

1. There are three p-orbitals and one s-orbital in each energy level, but an sp2-hybridized orbital uses more than one of the p-orbitals. This means that sp2- hybridization leaves one p orbital free to pi bond.

What is the bond order between the carbons in benzene (C₆H₆)?

1.5

How many σ bonds are in the structure of the organic molecule below?

16. Remember a single bond = 1 σ and a double bond = 1 σ + 1 π. This molecule contains 4 double bonds, so 4σ and 4π. This molecule contains 12 single bonds, so there are 12σ. Add these together to get 16σ.

A hybrid orbital set is shown below. How many unhybridized p orbitals does it have?

2

Use the blank MO diagram (below) to aid in answering the question. Calculate the bond order for BN.

2

Determine the number of rigid (π) bonds in linoleic acid.

3.

How many π bonds are in the structure of the organic molecule below?

4

How many electrons are shared between two atoms in a triple bond?

6. Two electrons are shared between two atoms in an individual bond, therefore in a triple bond 2 × 3 = 6 electrons are shared.

Which of the following has the shortest bond length?

A triple bond. - Triple bonds are shorter than double bonds and double bonds are shorter than single bonds.