1.
Which chemical bond involves sharing a pair of electrons between atoms in a molecule?
Correct Answer
C. A covalent bond
Explanation
A covalent bond involves the sharing of a pair of electrons between atoms in a molecule. In this type of bond, the atoms share electrons in order to achieve a stable electron configuration. This sharing of electrons creates a strong bond between the atoms, holding the molecule together.
2.
What is a covalent chemical bond where two lobes of one involved electron orbital overlap two lobes of the other?
Correct Answer
D. Pi bond
Explanation
A pi bond is a covalent chemical bond where two lobes of one involved electron orbital overlap two lobes of the other. Unlike a sigma bond, which forms when two atomic orbitals overlap head-on, a pi bond is formed when two parallel p orbitals overlap sideways. This type of bond is commonly found in double and triple bonds between atoms.
3.
A chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion is a (an)
Correct Answer
B. Ionic bond
Explanation
An ionic bond is formed when one atom loses an electron to become a positively charged ion (cation) and another atom gains that electron to become a negatively charged ion (anion). This attraction between the oppositely charged ions creates a strong bond between them, known as an ionic bond.
4.
Which of the following molecules is an example of a covalent compound?
Correct Answer
B. HCl
Explanation
A covalent compound is formed when atoms share electrons. In the case of hydrogen chloride (HCl), hydrogen and chlorine atoms form a covalent bond by sharing electrons. Hydrogen needs one more electron to achieve a stable configuration, and chlorine needs one electron to complete its outer shell. By sharing one electron each, they satisfy the octet rule (or duet rule for hydrogen) and form a stable molecule.
5.
A positively charged ion is a
Correct Answer
D. Cation
Explanation
A positively charged ion is called a cation because it has lost one or more electrons, leaving it with a net positive charge. Cations are formed when an atom loses electrons, resulting in an imbalance between the number of protons and electrons. This imbalance creates a positive charge, and cations are attracted to negatively charged particles. Therefore, the correct answer is cation.
6.
A negatively charged ion is a
Correct Answer
B. An anion
Explanation
A negatively charged ion is called an anion because it has gained one or more electrons, resulting in an overall negative charge. Anions are formed when atoms or molecules gain electrons, which causes an imbalance in the number of protons and electrons. This excess of electrons creates a negative charge, making the ion attracted to positively charged ions or molecules. Therefore, an anion is the correct term to describe a negatively charged ion.
7.
Which of the following elements commonly forms covalent bonds?
Correct Answer
A. Carbon
Explanation
Carbon commonly forms covalent bonds because it has four valence electrons in its outermost energy level. In order to achieve a stable electron configuration, carbon can share electrons with other atoms, forming covalent bonds. This allows carbon to form a variety of compounds, including organic molecules. Sodium, chlorine, and potassium, on the other hand, commonly form ionic bonds due to their tendency to gain or lose electrons to achieve a stable configuration.
8.
Which of the following is an example of a nonpolar covalent molecule?
Correct Answer
C. CO2 (carbon dioxide)
Explanation
CO2 (carbon dioxide) is an example of a nonpolar covalent molecule because it consists of two identical atoms of carbon bonded to one atom of oxygen. CO2 (carbon dioxide) is an example of a nonpolar covalent molecule because it consists of two identical atoms of carbon bonded to one atom of oxygen. The difference in electronegativities between C and O creates a dipole moment over the double bond between C and O; however, since carbon dioxide is a linear molecule with two identical C=O double bonds, the dipole moments of each bond cancel out. As a result, there is no separation of charge, making carbon dioxide nonpolar. In contrast, H2O (water), NH3 (ammonia), and HCl (hydrochloric acid) are polar molecules.
9.
In a covalent bond, electrons are shared between atoms to achieve:
Correct Answer
A. Stability
Explanation
In a covalent bond, electrons are shared between atoms to achieve stability. By sharing electrons, both atoms are able to fill their outermost energy level, resulting in a more stable arrangement. This sharing of electrons allows the atoms to achieve a lower energy state, reducing their overall reactivity and increasing their stability.
10.
Which of the following molecules exhibits a polar covalent bond?
Correct Answer
B. HF (hydrofluoric acid)
Explanation
HF (hydrofluoric acid) exhibits a polar covalent bond. In a polar covalent bond, the electrons are not shared equally between the atoms. In HF, fluorine is more electronegative than hydrogen, meaning it has a stronger pull on the shared electrons. As a result, the electrons spend more time around the fluorine atom, creating a partial negative charge on the fluorine and a partial positive charge on the hydrogen. This separation of charges gives rise to a polar covalent bond in HF.