The Chemical Basis of Life

Flashcards covering atoms, isotopes, bonds, water properties, and pH-related concepts from the lecture notes.

What are the smallest functional units of matter that form all chemical substances?

Atoms.

What is an element?

A substance consisting of only one type of atom; defined by its number of protons (atomic number).

Which subatomic particle carries a positive charge and is located in the nucleus?

Proton.

Which subatomic particle has no charge and is located in the nucleus?

Neutron.

Which subatomic particle carries a negative charge and orbits the nucleus?

Electron.

What is the atomic number?

The number of protons in the nucleus; in a neutral atom, it equals the number of electrons.

What are electron orbitals?

Regions surrounding the nucleus where electrons are likely to be found; include s (spherical) and p (dumbbell-shaped) orbitals.

What shapes do s and p orbitals have, and how many electrons can each orbital hold?

s orbitals are spherical; p orbitals are dumbbell-shaped; each orbital holds 2 electrons.

How many electrons can the first electron shell hold?

Two electrons (1s orbital).

How many electrons can the second electron shell hold?

Eight electrons (2s and three 2p orbitals).

How do electrons move between shells?

They move to higher shells by absorbing energy and to lower shells by releasing energy.

What is the electron configuration of Neon (atomic number 10)?

1s2 2s2 2p6.

In a nitrogen atom, how are electrons distributed between the first and second shells?

First shell holds 2 electrons (1s2); second shell holds 5 electrons (2s2 and three 2p electrons, with one in each 2p orbital).

What are valence electrons?

Electrons in the outermost shell that participate in bonding.

What does a period on the periodic table indicate?

The number of electron shells (energy levels) in the atoms of elements in that row.

Why do elements in a column have similar chemical properties?

Because they have the same number of valence electrons, determining bonding behavior.

What is the mass number?

The sum of protons and neutrons in the nucleus.

What is an isotope?

An element with the same number of protons but a different number of neutrons.

What is a radioisotope?

An unstable nucleus that decays, emitting energy and particles and becoming a different element.

What is Avogadro's number and what does a mole contain?

Avogadro's number is 6.02 × 10^23; a mole contains that many particles (atoms or molecules).

What is a Dalton (Da)?

A unit of atomic mass; 1 Da is 1/12 the mass of a carbon-12 atom.

What is the difference between mass and weight?

Mass is the amount of matter; weight depends on gravity.

What is covalent bonding?

Sharing of a pair of valence electrons between atoms; can be polar or nonpolar; forms molecules.

What is ionic bonding?

Electrostatic attraction between oppositely charged ions; forms salts like NaCl.

What is a hydrogen bond?

A weak attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom (usually O or N).

What are Van der Waals forces?

Weak interactions due to transient dipoles that occur when atoms are very close; contribute to macromolecule interactions.

What determines molecular shape and function?

The arrangement and number of bonds, plus bond angles; rotation around single bonds allows conformational changes.

What is a solution?

A homogeneous mixture of solute in solvent.

What is an aqueous solution?

A solution in which water is the solvent.

What is a hydration shell?

A sphere of water molecules surrounding a dissolved ion.

What is hydrophilic vs hydrophobic?

Hydrophilic substances dissolve in water; hydrophobic substances repel water.

What is an amphipathic molecule?

A molecule with both polar/ionic and nonpolar regions; can form micelles in water.

What is molarity (M)?

The number of moles of solute per liter of solution.

What is pH?

The negative logarithm of the hydrogen ion concentration; pH < 7 is acidic, pH > 7 is basic.

What is a buffer?

A weak acid and its conjugate base that resist pH changes by releasing or absorbing H+.