Chemical Bonds and Molecules

Practice flashcards covering types of chemical bonds, molecular structure, and interatomic forces from the lecture notes on '2.2 Chemical Bonds and Molecules'.

What is a molecule?

Two or more atoms bonded together.

What is a compound?

A molecule composed of two or more different elements.

What are emergent properties in the context of compounds?

The characteristics of a compound differ greatly from those of its constituent elements.

What holds atoms together in molecules?

Chemical bonds.

How are covalent bonds formed?

By atoms sharing a pair of electrons to fill their outer shells.

What fundamental principle describes the stability of atoms regarding their outer electron shells?

Atoms tend to be most stable when their outer shells are filled with electrons.

How is a covalent bond represented in a structural formula?

By a line indicating a pair of shared electrons.

What determines the characteristic number of covalent bonds an atom forms?

The number of electrons required to fill its outer shell.

What is the octet rule?

Many atoms are most stable when they have eight electrons in their outermost electron shell (hydrogen typically needs two electrons).

What occurs in a double bond?

Atoms share two pairs of electrons (four electrons) rather than one pair.

What is electronegativity?

A measure of an atom's ability to attract electrons in a bond with another atom.

What defines a nonpolar covalent bond?

A covalent bond between atoms with similar electronegativities (difference less than 0.4), where electrons are shared fairly equally.

What defines a polar covalent bond?

A covalent bond between atoms with an electronegativity difference from 0.4 to 1.8, where shared electrons are more likely to be closer to the atom with higher electronegativity, creating partial positive and negative charges.

How can a molecule with polar covalent bonds be nonpolar overall?

If the bond angles are symmetric, causing the charges to be equally distributed across the molecule (e.g., carbon dioxide).

What is a hydrogen bond?

A weak interaction formed when a hydrogen atom in one polar molecule is electrically attracted to an electronegative atom (like oxygen or nitrogen) in another or the same polar molecule.

Why are hydrogen bonds important, despite being individually weak?

Collectively, many hydrogen bonds provide a strong force that can maintain the three-dimensional structure of large molecules and allow for reversible interactions between molecules.

What are van der Waals dispersion forces?

Temporary attractive forces between molecules, even weaker than hydrogen bonds, that arise from fleeting electrical attractions caused by random, uneven distributions of electrons.

What is an ion?

An atom or molecule that has gained or lost one or more electrons, acquiring a net electric charge.

What is a cation?

An ion with a net positive charge, formed when an atom loses electrons.

What is an anion?

An ion with a net negative charge, formed when an atom gains electrons.

How is an ionic bond formed?

When a cation binds to an anion, typically between atoms that differ greatly in their electronegativities, involving a transfer of electrons.

Why is a molecule's shape important to its ability to interact with other molecules?

A molecule's three-dimensional, flexible shape contributes to its biological properties, as specific shapes allow for binding and interaction, and shape changes can trigger biological activity.