Basic Chemistry of Life

Practice flashcards covering atomic structure, chemical bonding, water properties, pH, and functional groups.

What are the three primary sub-atomic particles that compose an atom, and where are they located?

Protons (positively charged) and neutrons (neutral) are located in the nucleus, while electrons (negatively charged) are located in orbitals surrounding the nucleus.

Which six elements make up $99\%$ of the atoms in all living organisms?

Oxygen ($\text{O}$), Carbon ($\text{C}$), Hydrogen ($\text{H}$), Nitrogen ($\text{N}$), Calcium ($\text{Ca}$), and Phosphorus ($\text{P}$).

What are isotopes, and why do some isotopes release radiation?

Isotopes are naturally occurring forms of an element with the same number of protons but a different number of neutrons. The extra neutrons make some atoms unstable, causing them to release energetic particles (radiation) from their nuclei to achieve a stable state.

What are the characteristics and stopping materials for alpha, beta, and gamma radiation?

Alpha radiation is slow-moving and stopped by paper or skin; beta radiation is faster-moving and stopped by foil or glass; gamma radiation travels at light speed and is stopped by concrete, lead, or steel.

What type of radiation is emitted when an unstable radioactive isotope loses two protons and two neutrons?

Alpha radiation.

What feature of an atom determines its chemical reactivity?

The number of electrons in its outermost (valence) electron shell. Atoms with full valence shells are non-reactive, while atoms with partly full valence shells form chemical bonds to fill their orbitals.

How does a molecule differ from a compound?

A molecule consists of two or more atoms chemically joined by covalent bonds (e.g., $\text{H}_2$ or $\text{H}_2\text{O}$). A compound consists of two or more atoms of different elements chemically joined by covalent or ionic bonds (e.g., $\text{NaCl}$).

What is the difference between a nonpolar covalent bond and a polar covalent bond?

In a nonpolar covalent bond, electrons are shared equally and the bond is symmetrical (e.g., $\text{H}_2$). In a polar covalent bond, electrons are shared unequally because one atom is more electronegative, resulting in an asymmetrical bond with partial charges (e.g., $\text{H}_2\text{O}$).

What is electronegativity, and how does it affect charge distribution in a molecule?

Electronegativity is the measure of how strongly an atom holds bonding electrons. The more electronegative atom holds electrons more tightly, acquiring a partial negative charge ($\delta^-$), while the less electronegative atom acquires a partial positive charge ($\delta^+$).

What are cations and anions, and how are they formed?

Cations are positively charged ions formed when an atom loses electrons (e.g., $\text{Na}^+$). Anions are negatively charged ions formed when an atom gains electrons (e.g., $\text{Cl}^-$).

What holds an ionic bond together, and how do polar molecules affect ionic compounds?

Ionic bonds are held together by electrostatic attraction between oppositely charged ions. Polar molecules like water easily disrupt ionic bonds by pulling the ions apart into solution.

What factor determines whether two atoms will form a covalent bond or an ionic bond?

The difference in electronegativity between the two atoms.

What is an electrolyte?

An electrolyte is any substance that exists in an ionized state in water and conducts electricity when in solution (e.g., $\text{NaCl} + \text{H}_2\text{O} \rightarrow \text{Na}^+ + \text{Cl}^- + \text{H}_2\text{O}$).

What is a hydrogen bond?

A hydrogen bond is a weak attraction between a partially positive hydrogen atom ($\delta^+$) of one polar molecule and a highly electronegative atom ($\delta^-$) (such as oxygen or nitrogen) in another molecule, formed without sharing or transferring electrons.

How do water molecules orient themselves around $\text{Na}^+$ and $\text{Cl}^-$ ions when table salt dissolves in water?

The partially negative oxygen atom ($\delta^-$) of water is nearest to the positively charged sodium ion ($\text{Na}^+$), while the partially positive hydrogen atoms ($\delta^+$) are nearest to the negatively charged chloride ion ($\text{Cl}^-$).

What is the difference between hydrophilic and hydrophobic substances?

Hydrophilic substances are ions or polar molecules that readily interact with water's partial charges (e.g., sugar). Hydrophobic substances are nonpolar molecules that do not have an affinity for water (e.g., oils).

How do adhesion and cohesion differ in water?

Adhesion refers to water molecules forming hydrogen bonds with other polar or charged substances, whereas cohesion refers to water molecules forming hydrogen bonds with each other.

What creates the high surface tension of water?

Cohesive forces at the air-water interface cause surface water molecules to bind more tightly to each other than to air molecules.

What is capillary action, and what forces drive it?

Capillary action is the flow of water through narrow spaces when adhesion to a polar surface is stronger than cohesion. It is driven by adhesion, cohesion, surface tension, and gravity.

Why does ice float on liquid water?

As water freezes, decreased kinetic energy causes stable hydrogen bonds to form a regular lattice structure with more space between molecules, making solid ice less dense than liquid water.

Why does water have a high specific heat, and why is this property ecologically important?

Water requires a large amount of heat energy to break its numerous hydrogen bonds to raise its temperature by $1\,^{\circ}\text{C}$. This stabilizes temperatures in large bodies of water and moderates coastal climates.

How does water's high heat of vaporization facilitate evaporative cooling?

Body heat increases the kinetic energy of water molecules in sweat, breaking hydrogen bonds and allowing high-energy water molecules to escape as vapor, thereby removing heat from the skin surface.

What molecule is formed when a dissociated hydrogen ion ($\text{H}^+$) associates with another water molecule?

A hydronium ion ($\text{H}_3\text{O}^+$), formed via the reaction $\text{H}_2\text{O} + \text{H}_2\text{O} \rightleftharpoons \text{H}_3\text{O}^+ + \text{OH}^-$.

How is pH defined mathematically, and how does $[\text{H}^+]$ relate to the pH value?

pH is defined as $\text{pH} = -\log[\text{H}^+]$. A higher hydrogen ion concentration ($[\text{H}^+]$) results in a lower pH value on the 1-14 scale.

How do acidic, basic, and neutral solutions compare in terms of $[\text{H}^+]$, $[\text{OH}^-]$, and pH values?

Acidic solutions have $[\text{H}^+] > [\text{OH}^-]$ and $\text{pH} < 7$; basic solutions have $[\text{H}^+] < [\text{OH}^-]$ and $\text{pH} > 7$; neutral solutions have $[\text{H}^+] = [\text{OH}^-]$ and $\text{pH} = 7$.

What three homeostatic mechanisms maintain pH balance in human body fluids?

Chemical buffers (such as bicarbonate), respiratory mechanisms (regulating $\text{CO}_2$ and bicarbonate), and renal mechanisms (kidneys absorbing or secreting $\text{H}^+$).

Why is carbon considered a versatile building block, and what distinguishes organic from inorganic compounds?

Carbon has four valence electrons and can form single and double bonds in diverse shapes. Organic compounds contain mostly carbon, whereas inorganic compounds contain little or no carbon.

What is the formula and function of an amino functional group?

The amino group formula is $-\text{NH}_2$ (or $-\text{NH}_3^+$ when ionized). It acts as a base by accepting a proton ($\text{H}^+$) in solution.

What is the formula and function of a carboxyl functional group?

The carboxyl group formula is $-\text{COOH}$ (or $-\text{COO}^-$ when ionized). It acts as an acid by releasing a proton ($\text{H}^+$) in solution.

How do aldehydes and ketones differ regarding their carbonyl group ($\text{C}=\text{O}$) placement?

Aldehydes have the carbonyl group ($\text{C}=\text{O}$) at the end of a carbon skeleton, whereas ketones have the carbonyl group in the interior of the carbon skeleton.

What are the key functions of hydroxyl, phosphate, and sulfhydryl functional groups?

Hydroxyl ($-\text{OH}$) acts as a weak acid; phosphate ($-\text{PO}_4^{2-}$) functions in energy transfer, nucleic acids, and buffering; sulfhydryl ($-\text{SH}$) links via covalent disulfide bonds ($\text{S}-\text{S}$) in proteins.

What are the chemical properties of a methyl functional group?

The methyl group ($-\text{CH}_3$) is nonpolar, highly stable, non-reactive, hydrophobic, and does not form hydrogen bonds or interact with water.