Chemistry Chapter: Atomic Structure and Bonds

Atomic Structure and Isotopes

• Electrons orbit the nucleus in an electron cloud, contributing to the atom's negative charge.
• Mass number is the sum of protons and neutrons; neutrons are mass-heavy but electrically neutral.
• Isotopes have the same number of protons but differing neutrons, leading to different mass numbers.
• Radioisotopes emit radiation and decay at a characteristic rate called half-life.
• Atomic weight is crucial for chemical reactions, and is used to measure chemicals.

Chemical Properties and Ions

• Atoms are neutral if they have equal protons and electrons; an imbalance creates ions (charged atoms).
• Energy levels, analogous to shells, dictate the number of electrons surrounding the atom: Level 1 holds 2, Levels 2 and 3 hold 8 each.
• Atoms with unfilled outer energy levels are reactive; filled outer levels are inert.

Chemical Bonds

• Chemical bonds are formed to stabilize reactive atoms by gaining, losing, or sharing electrons.
• Types of chemical bonds:
  • Ionic Bonds: Formed between oppositely charged ions (cations and anions), enabling the conduction of electricity in solution (electrolytes).
  • Covalent Bonds: Atoms share electrons, creating molecules; single bonds share one pair while double bonds share two pairs.
  • Hydrogen Bonds: Weak attractions between polar molecules; significant in the structure of proteins and DNA, and contribute to water's unique properties.

Chemical Reactions and Energy

• Chemical reactions involve reactants transforming into products, contributing to metabolism.
• Chemical energy in bonds is potential; energy conversion results in some loss as heat.
• Salts dissociate into ions in solution but have negligible effects on pH.

Buffers and pH Control

• Buffers stabilize pH by removing or replacing H+ ions, essential for maintaining physiological conditions.

Organic Compounds

• Comprised mostly of carbon, hydrogen, and oxygen; classes include carbohydrates, lipids, proteins, and nucleic acids, with functional groups enhancing molecular interactions.

Carbohydrates

• Organic molecules with a ratio of 1:2:1 for carbon, hydrogen, and oxygen; categorized into:
  • Monosaccharides: Single sugars (e.g., glucose).
  • Disaccharides: Two sugars linked; require hydrolysis for use (e.g., sucrose).
  • Polysaccharides: Long chains of sugars; examples include cellulose (indigestible), starch (digestible), and glycogen (animal glucose storage).

Lipids

• Hydrophobic molecules primarily made of carbon and hydrogen; five main classes:
  • Fatty Acids: Differentiated by saturation levels (saturated, monounsaturated, polyunsaturated).
  • Eicosanoids: Derived from arachidonic acid; involved in inflammation and hormonal signaling.
  • Glycerides: Comprises monoglycerides, diglycerides, and triglycerides; provide energy, insulation, and protection.
  • Steroids: Composed of four carbon rings; includes cholesterol and sex hormones.
  • Phospholipids and Glycolipids: Form cell membrane structures, possessing both hydrophilic heads and hydrophobic tails.

Proteins

• Composed of carbon, hydrogen, oxygen, and nitrogen; crucial for all bodily functions and serve as cell factories for protein synthesis.