Atomic Structures and Electron Shells

Atomic Structure and Chemical Bonds

• Atoms have electron "shells" surrounding the nucleus, with each shell having a specific electron capacity.
• The first shell can hold 2 electrons, while the second and third shells can accommodate 8 electrons each.
• Valence shells desire to be full, leading to chemical stability.
• The octet rule explains that atoms tend to lose, gain, or share electrons to attain full outer shells.

Chemical Compounds and Bonds

• Chemical compounds consist of stable combinations of two or more elements in fixed ratios, typically satisfying the octet rule.
• Two main types of chemical bonds form these compounds: ionic and covalent bonds.
• Ionic compounds are structured around ions, which are charged atoms resulting from the loss or gain of electrons.

Ions and Their Functions

• Cations are positive ions (e.g., Na+, K+), while anions are negative (e.g., Cl-, PO3-).
• Ions act as electrolytes, dissociating in water and conducting electrical currents.

Covalent Bonding

• Covalent bonds occur when atoms share electrons from their outermost shells.
• Molecular compounds consist of two or more atoms linked by covalent bonds (e.g., CO2) while molecular oxygen (O2) is simply termed a molecule.
• Covalent bonds can be single (one pair of electrons shared), double (two pairs), or triple (three pairs).

Properties of Water

• Water is essential for life; it has high specific heat and high heat of vaporization, stabilizing body temperature.
• High specific heat prevents drastic temperature changes, while high heat of vaporization allows the body to cool effectively through sweating.
• Water’s high surface tension helps prevent lung alveoli from collapsing and provides lubrication in various body systems.

pH and Biological Relevance

• Water has a neutral pH, but body fluids can vary with the addition of acids or bases.
• The pH range in the body is generally around 7.0-7.4, with exceptions in specific organs.

Nucleic Acids and Their Functions

• Nucleotides, the building blocks of nucleic acids, consist of a 5-carbon sugar, phosphate group, and nitrogenous base.
• DNA stores and transmits hereditary information, while RNA is critical for protein synthesis.

Energy and Metabolism

• Water, comprising around 60% of the body, serves as a solvent for biochemical reactions.
• Body temperature (98.6°F or 37°C) and a stable pH of 7.0-7.4 enable efficient enzymatic reactions.

Types of Chemical Reactions

• Decomposition reactions break down compounds into simpler structures (AB → A + B).
• Synthesis reactions combine structures to form larger entities (A + B → AB).
• Exchange reactions involve swapping groups between chemical structures (AB + C → A + BC).

Enzymes and Their Role

• Enzymes are globular proteins that act as catalysts, increasing reaction rates without altering the equilibrium.
• Enzymes have specific active sites that accommodate particular substrates, facilitating precise biochemical reactions.

Cellular Respiration

• Cellular respiration includes glycolysis, the citric acid cycle, and the electron transport chain.
• ATP production totals approximately 38 molecules per glucose, with glycolysis and the electron transport chain contributing significantly to ATP yield.
• ATP also serves as a regulatory molecule, inhibiting various enzymes during cellular respiration through negative feedback.

This quiz covers the fundamental concepts of atomic structures, focusing on the arrangement of electrons in shells around the nucleus. It includes topics such as the capacity of each shell, the importance of filling inner shells first, and the significance of valence shells in chemical stability according to the octet rule.