Chapter 2: The Chemical Context of Life - Practice Flashcards

A set of practice flashcards covering key concepts from Chapter 2: The Chemical Context of Life.

What determines an atom's identity?

The number of protons in the nucleus (the atomic number).

What is an element?

A substance that cannot be broken down into other substances by chemical reactions; defined by its number of protons.

What is a compound?

A substance consisting of two or more different elements in a fixed ratio.

Which four elements make up approximately 96% of living matter?

Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N).

What is a trace element?

An element required in minute quantities; some are essential to life (e.g., iron, iodine).

What is an emergent property of a compound?

A compound has characteristics different from those of its constituent elements.

What is an isotope?

Atoms of the same element with different numbers of neutrons, giving different mass numbers.

What unit is used to express atomic mass?

The dalton (atomic mass unit, amu).

What is the mass number of an atom?

The total number of protons and neutrons in the nucleus.

What is atomic mass?

A weighted average of the masses of an element's isotopes, measured in daltons.

What is radiometric dating?

Dating fossils by measuring radioactive decay and half-lives of isotopes.

What is a half-life?

The time required for half of a radioactive isotope to decay.

What is electronegativity?

An atom's attraction for the electrons in a covalent bond, determining bond polarity.

What is a polar covalent bond? Give an example.

A covalent bond where electrons are shared unequally; e.g., the O–H bonds in water.

What is a nonpolar covalent bond? Give an example.

A covalent bond where electrons are shared equally; examples: H2, O2.

What is an ionic bond?

An attraction between oppositely charged ions formed by transfer of electrons; e.g., NaCl.

What are cations and anions?

Cations are positively charged ions; anions are negatively charged ions.

What are weak interactions and why are they important?

Hydrogen bonds and van der Waals interactions; they help maintain molecular shapes and interactions in biology.

What determines a molecule's shape in biology?

The arrangement of atoms' valence orbitals; covalent bonds create hybrid orbitals that shape molecules like H2O and CH4.

What is a hydrogen bond?

A noncovalent attraction between a hydrogen atom with a partial positive charge and an electronegative atom with a partial negative charge.

What is the difference between a molecule and an ionic compound?

A molecule is two or more covalently bonded atoms; an ionic compound is a crystal lattice of ions held by ionic bonds (not discrete molecules).

What is the photosynthesis equation summarized?

6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2; matter is rearranged with energy from sunlight.

What is chemical equilibrium?

A dynamic state where forward and reverse reaction rates are equal, leading to stabilized concentrations of reactants and products.