Atomic Structure and Bonding Quiz

Atomic Structure and Bonding

• Atoms are composed of protons (+ charge), neutrons (no charge), and electrons (- charge). Protons and neutrons reside in the nucleus; electrons orbit the nucleus.
• Atomic number = number of protons; mass number = protons + neutrons. Knowing these, you can calculate the number of each subatomic particle in an atom.
• Isotopes are atoms of the same element with different numbers of neutrons. This alters the mass number.
• Example of an isotopic application in human health: radioactive isotopes are used in medical imaging and cancer treatment (e.g., iodine-131 for thyroid disorders).
• Electron shells have specific capacities: first shell holds 2 electrons, second shell holds 8, and third shell holds 8 (initially).
• A stable atom has all its electron orbitals completely filled.

Ionic and Covalent Bonds

• Ionic bonds form when one atom transfers electrons to another, creating oppositely charged ions that attract. Example: NaCl (sodium chloride).
• Covalent bonds form when atoms share electrons. Example: H₂O (water).
• Electronegativity is an atom's ability to attract electrons in a chemical bond.
• Polar covalent bonds form when electrons are shared unequally due to differences in electronegativity. Water (H₂O) is an example.
• Nonpolar covalent bonds form when electrons are shared equally due to similar electronegativities. An example is H₂ (hydrogen gas).

Water and Solutions

• Hydrogen bonds form between the slightly positive hydrogen atoms of one water molecule and the slightly negative oxygen atom of another. This polarity gives water unique properties.
• An electrolyte is a substance that dissociates in water to form ions, which are essential for many bodily functions.
• Acids release H+ ions in solution, while bases release OH– ions.
• pH is inversely related to H+ concentration. A lower pH (e.g. 2) signifies a higher H+ concentration compared to a higher pH (e.g. 4). A whole number change in pH represents a 10-fold difference in H+ concentration.
• A buffer solution resists changes in pH by absorbing or releasing H+ ions. Important for biological systems to maintain stable pH.

Organic Molecules

• Carbon atoms can form four covalent bonds, a crucial feature for the diversity of organic molecules.
• Organic molecules are composed primarily of carbon and hydrogen, with other elements like oxygen, nitrogen, and phosphorus also present.
• Functional groups are specific arrangements of atoms within molecules that give them characteristic chemical properties. These groups determine how molecules interact.
• Monomers are small, repeating units; polymers are large molecules formed from many monomers linked together.
• Reactants are substances that undergo a chemical reaction, and products are the resulting substances.
• Dehydration reactions link monomers together and release water; hydrolysis reactions break polymers apart by adding water.
• Four categories of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Atomic composition is primarily carbon, hydrogen, and oxygen.
• Functions include energy storage, structural support, and cell recognition.
• Examples include sugars, starches, and cellulose.
• Subcategories: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

Lipids

• Atomic composition: primarily carbon, hydrogen, and oxygen (with less oxygen than carbohydrates).
• Functions: energy storage, insulation, and structural components of cell membranes.
• Examples: fats, oils, phospholipids, and steroids.
• Subcategories: fatty acids, phospholipids, and steroids.

Proteins

• Atomic composition: carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
• Functions: structural support, enzymes, transport, hormones, and defense.
• Examples: keratin, hemoglobin, enzymes.
• Structure: amino acid—> polypeptide chain—> protein
• Peptide bonds link amino acids.
• Protein structure (primary, secondary, tertiary, quaternary) describes the organization of amino acid chains. Denaturation alters a protein's shape, rendering it inactive.
• Protein denaturation examples: heat, pH changes, etc.

Nucleic Acids

• Atomic composition: carbon, hydrogen, oxygen, nitrogen, and phosphorus.
• Functions: store and transmit genetic information.
• Examples: DNA, RNA.
• DNA and RNA differ structurally and functionally.
• Nucleotide structure: sugar, phosphate group, and a nitrogenous base.
• Nitrogenous bases: adenine, guanine, cytosine, and thymine (or uracil in RNA). They have specific pairing rules.