The Chemical Foundation of Life

A set of practice flashcards covering key concepts from the lecture notes on atomic structure, periodic properties, chemical bonding, water chemistry, acids/bases, and organic functional groups.

What are the four fundamental assumptions of modern atomic theory?

1) All matter is composed of atoms; 2) Atoms of a given element differ from atoms of all other elements; 3) Chemical compounds consist of atoms in fixed ratios; 4) Chemical reactions change only the way atoms are combined; the atoms themselves are unchanged.

Which four elements make up 96.5% of body weight?

Oxygen, Carbon, Hydrogen, and Nitrogen.

What is a chemical compound?

A substance consisting of two or more elements in a fixed ratio with properties different from its constituent elements.

What is an atomic number?

The number of protons in an atom; identifies the element.

What is the mass number?

The total number of protons and neutrons in an atom.

Why are atoms neutral overall?

Because the number of positively charged protons equals the number of negatively charged electrons.

What are isotopes?

Atoms of the same element that differ in the number of neutrons.

What are radioisotopes and their applications?

Isotopes that decay spontaneously; used in dating fossils, tracing metabolic processes, and diagnostic medical imaging.

What is atomic weight?

The weighted average mass of an element’s atoms, reflecting the natural isotopes.

How is atomic weight calculated?

Atomic weight = sum of (isotope abundance × isotope mass) for all naturally occurring isotopes.

What are the two regions of an atom?

The nucleus (protons and neutrons) and the electron cloud (electrons in orbit around the nucleus).

What are protons, neutrons, and electrons referred to as?

Subatomic particles.

Where are protons and neutrons located in an atom?

In the nucleus.

Where are electrons located in an atom?

In orbit around the nucleus in the electron cloud.

What is the first shell’s maximum electron capacity?

2 electrons.

How many electrons can the second shell hold?

8 electrons.

How many electrons can the third shell hold?

18 electrons.

What are the four subshell types?

s, p, d, and f.

How many orbitals does an s subshell have and how many electrons can it hold?

1 orbital; 2 electrons.

How many orbitals does a p subshell have and how many electrons can it hold?

3 orbitals; 6 electrons.

What are the key principles of electron configuration?

Aufbau principle (lowest energy orbitals fill first), Pauli exclusion principle (max 2 electrons per orbital with opposite spins), Hund’s rule (one electron in each degenerate orbital before pairing).

What is the valence shell?

The outermost, highest-energy electron shell.

What are valence electrons?

Electrons in the outermost shell; determine an element’s chemical properties.

What is a covalent bond?

A bond formed by sharing electrons between atoms.

What is a molecule?

A group of atoms held together by covalent bonds.

What is the octet rule?

Main-group elements tend to have eight valence electrons (two for hydrogen) achieved through covalent bonding.

What are single, double, and triple covalent bonds?

Single bond = sharing one electron pair; double bond = two pairs; triple bond = three pairs.

What is a polar covalent bond?

A covalent bond in which electrons are shared unequally due to electronegativity differences.

What is electronegativity?

An atom’s tendency to attract electrons in a bond.

What is a dipole moment?

A separation of charge within a molecule due to bond polarity, giving a positive and a negative end.

What is a nonpolar covalent bond?

A covalent bond in which electrons are shared equally (small electronegativity difference).

What is an ion?

A charged particle formed by loss or gain of electrons.

What is a cation?

A positively charged ion formed by the loss of electrons.

What is an anion?

A negatively charged ion formed by the gain of electrons.

What is ionization energy?

The energy required to remove one electron from a gaseous atom.

What is electron affinity?

The energy released when adding an electron to a gaseous atom.

What is an ionic bond?

Electrostatic attraction between ions of opposite charge.

What happens when an ionic compound dissolves in water?

Ions become surrounded by hydration shells formed by water molecules.

What is a hydration shell?

A cluster of water molecules surrounding an ion.

What is a hydrophilic substance?

A substance with an affinity for water.

What is a hydrophobic substance?

A substance with little or no affinity for water.

What is pH?

A measure of the hydrogen ion concentration in a solution.

What is an acid?

A substance that increases H+ concentration in solution (pH < 7).

What is a base?

A substance that decreases H+ concentration in solution (pH > 7).

What environmental issues relate to water chemistry discussed in the notes?

Acid rain and the greenhouse effect; CO2 forms carbonic acid in water, contributing to ocean acidification and climate warming.

Why is water essential to life?

Water is polar, forms hydrogen bonds, is a versatile solvent, and has high heat capacity, helping regulate temperature.

What are functional groups in organic molecules?

Specific groups of atoms that impart characteristic chemical reactivity to carbon skeletons.