Atomic Structure and Chemical Bonds

This set of vocabulary flashcards covers atomic structure, electron configuration, and various types of chemical bonding as presented in the lecture notes.

Atoms

The building blocks of all matter in the Universe, consisting of electrons, protons, and neutrons.

Electrons

Negatively charged subatomic particles that are the smallest of the three and are found in orbitals within shells, possessing a mass of $0$.

Nucleus

The center of the atom that usually consists of an equal number of protons (positively charged) and neutrons (no charge).

Atomic Number

The number of protons in an atom, which is equal to the number of electrons for any given atom.

Atomic Mass Number

The sum of the number of protons and neutrons in an atom, where protons and neutrons each have a mass of $1$.

Orbital

The physical region or space where an electron is expected to be present, capable of being occupied by a maximum of two electrons.

Ground State

The lowest energy level at which orbitals exist.

s orbital

The orbital with the lowest energy, represented by sharp spectroscopic lines.

p orbital

The second type of orbital, represented by principle spectroscopic lines.

First shell

The innermost shell of an atom which has one orbital ($1s$) and can be occupied by a maximum of two electrons.

Second shell

An electronic shell that has four orbitals (one $2s$, and three $2p$ orbitals), allowing for a maximum of eight electrons.

Hund's Rule

The rule stating that each electron will first fill all degenerate orbitals with similar energy before pairing with another electron in a half-filled orbital.

Degenerate Orbitals

Orbitals that possess similar energy levels.

Chemical Bond

An attraction between atoms that results in the formation of a chemical compound (molecule) containing two or more atoms.

Covalent Bond

A chemical bond resulting from the equal sharing of electrons between two atoms, characterized by high stability due to high bond energies.

Single Covalent Bond

A bond representing the sharing of two valence electrons, such as the bond in the hydrogen molecule ($H_2$) or the four $C-H$ bonds in methane ($CH_4$).

Double Covalent Bond

A bond resulting from the sharing of two pairs of electrons between atoms, as seen in ethylene ($C_2H_4$) and carbon dioxide ($CO_2$).

Triple Covalent Bond

A bond resulting from the sharing of three pairs of electrons, such as the bond between the two nitrogen atoms in a nitrogen molecule ($N_2$).

Noncovalent Interactions

A class of four main interactions in biological systems: ionic bonds, hydrogen bonds, van der Waals interactions, and hydrophobic interactions.

Ionic Bond

A bond formed by the attraction of oppositely charged atoms or groups of atoms (ions).

Cation

A positively charged ion that is attracted to the negatively charged 'cathode' in an electric field.

Anion

A negatively charged ion that is attracted to the positively charged 'anode' in an electric field.

Hydrogen Bond

The interaction of a partially positively charged hydrogen atom in a dipolar molecule with unpaired electrons from another atom.

Van der Waals Interactions

Weak, nonspecific attractive forces resulting from temporary and random fluctuations in the distribution of the electrons of any atom.

Hydrophobic Effect

A phenomenon where nonpolar molecules aggregate in water, forcing the nonpolar surfaces to face each other to minimize contact with the aqueous environment.