Concept 2.3: An element's properties depend on the structure of its atoms

Flashcards from Concept 2.3 of Pearson's Campbell Biology, Twelfth Edition.

Chemical bonds

The attractions between atoms through sharing or transferring electrons created to complete an atom’s valence shell

Covalent bonds

The sharing of a pair of valence electrons by two atoms, counting as part of each atom’s valence shell

Molecule

Two or more atoms held together by covalent bonds

Single bond

A single covalent bond; the sharing of one pair of valence electrons

• Notated with lines like H—H to represent bonds, or molecular formulae like H₂

Double bond

A double covalent bond; the sharing of two pairs of valence electrons

Valence

The atom’s bonding capacity between atoms of the same or different elements

Compound

A combination of two or more different elements held together by covalent or ionic bonds

Electronegativity

An atom’s attraction for the electrons in a covalent bond; higher levels of this pulls electrons toward itself

Nonpolar covalent bonds

Bonds where the atoms share electrons equally

Polar covalent bonds

Bonds where one atom is more electronegative and do not share electrons equally, creating a partial positive or negative charge for each atom or molecule

Ions

The result of ionic bonds in atoms where an electron is transferred and not shared between two atoms in a bond

Cation

A positively charged ion

Anion

A negatively charged ion

Ionic bond

The attraction of cations and anions to form a bond

Ionic compounds (salts)

Compounds formed by ionic bonds, such as sodium chloride (NaCl)

• NaCl itself is not a molecule but instead describes the ratio of atoms of a specific element in the bond

• Salts dissolve easily in a solute, like water

Hydrogen bond

A bond between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom, typically seen as other oxygen or nitrogen atoms

Van der Waals interactions

The uneven accumulation of electrons in one part of a molecule, creating attractions that are close together and can be strong enough to create bonds in organisms

• Geckos are able to walk up walls

Molecular size and shape

These are key to its function, determined by the positions of its atoms’ orbitals

• Similarly shaped molecules may serve similar purposes due to this, as is in the case of opiates and endorphins in the brain’s receptors