CHEM 107 General & Organic Chemistry COMPLETED EXAM 2026 (12pages)

What is the difference between an atom and an ion? Give an example of each. - An atom is the smallest unit of matter that retains the identity of an element. An ion is an atom that has gained or lost one or more electrons, resulting in a net electric charge. For example, a hydrogen atom has one proton and one electron, while a hydrogen ion has only one proton and no electrons. - Rationale: This question tests the basic definition and concept of atoms and ions, which are important for understanding chemical reactions and interactions in the body. What is the difference between atomic number and mass number? How are they related to the number of protons, neutrons, and electrons in an atom? - Atomic number is the number of protons in the nucleus of an atom, which determines its identity as an element. Mass number is the sum of protons and neutrons in the nucleus of an atom, which determines its mass and isotopic variation. The number of electrons in a neutral atom is equal to the atomic number. For example, carbon has an atomic number of 6, which means it has 6 protons and 6 electrons. Carbon-12 has a mass number of 12, which means it has 6 protons and 6 neutrons. Carbon-14 has a mass number of 14, which means it has 6 protons and 8 neutrons. - Rationale: This question tests the understanding of atomic number and mass number, which are important for identifying elements and isotopes, as well as calculating atomic mass and molecular weight. What is the difference between covalent and ionic bonds? Give an example of each. - Covalent bonds are formed when atoms share one or more pairs of electrons to achieve stability. Ionic bonds are formed when atoms transfer one or more electrons to each other to achieve stability. For example, water (H2O) is a covalent compound, where two hydrogen atoms share one electron each with one oxygen atom. Sodium chloride (NaCl) is an ionic compound, where one sodium atom loses one electron to one chlorine atom, resulting in positive and negative ions that attract each other. - Rationale: This question tests the understanding of covalent and ionic bonds, which are important for explaining the formation and properties of molecules and compounds. What is the difference between polar and nonpolar covalent bonds? How do they affect the solubility and reactivity of molecules? - Polar covalent bonds are formed when atoms share electrons unequally, resulting in partial charges on the atoms. Nonpolar covalent bonds are formed when atoms share electrons equally, resulting in no charges on the atoms. Polar molecules tend to be soluble in polar solvents (such as water) and reactive with other polar molecules or ions. Nonpolar molecules tend to be insoluble in polar solvents (such as water) and reactive with other nonpolar molecules or forces (such as van der Waals forces). - Rationale: This question tests the understanding of polar and nonpolar covalent bonds, which are important for predicting the behavior and interactions of molecules in different environments.