U3 revision key terms Flashcards
Ionic bond
Electrostatic attraction between oppositely charged ions that holds the ions in close proximity.
The ionic bond forms between metal +non-metal
Electrostatic attraction
A non-contact attractive force that occurs between particles of opposite charge.
静电吸引力
Binary Ionic compound
Is Composed of ions of two different elements
Lattice
A three-dimensional regular repeating arrangement of ions, atoms or molecules in a crystalline solid.
Metallic Bond
The electrostatic attraction between a lattice of positive metal ions and a sea of delocalized electrons.
The metallic bond forms between metal + metal
Delocalized electrons 游离电子
An electron that is not associated with one specific atom and is free to move within the molecular structure.
Alloys 合金
Homogeneous mixtures of a metal and other metals or non-metals.
Covalent bond
The electrostatic force of attraction between two positive nuclei and a shared pair of electrons.
The covalent bond forms between non-metals + non-metals
Polar covalent bond
极性共价键
A bond which has a partially positive end and a partially negative end due to asymmetrical electron distribution caused by the difference in electronegativity of the two bonded species.
A polar covalent bond has an asymmetric bonding orbital electron density function with non-equal sharing of the bonding electrons
non-polar covalent bond
非极性共价键
A covalent bond formed between two atoms with equal electronegativity values which results in equal sharing of the electrons in their bond.
A nonpolar covalent bond has a symmetric bonding orbital electron density function with equal sharing of the bonding electron.
Electronegativity (χ)
the ability of an atom in a molecule or an ion to attract electrons to itself
Dipole (movement)
The two separated opposite electric charges, δ+ and δ-, existing in a polar bond.
Covalent Network Solids
Covalent network solids are composed of atoms covalently bonded together into a three-dimensional network or layers of two-dimensional networks. Due to the strength of the covalent bonds, covalent network solids have high melting points.
(e.g 3d: Diamond , Silica. (hard and rigid) 2d: graphite (soft due to the easy slide past each other ))
Coordination Bond
(also called a dative covalent bond) is a covalent bond (a shared pair of electrons) in which both electrons come from the same atom
Octet rule
The tendency of an atom to achieve stability by ensuring its valence shell is full, either by gaining, losing or sharing electrons.
VSEPR theory
Valence Shell Electron Pair Repulsion theory: A theory used to explain and predict molecular geometry, based on numbers of electron domains (bonded and non-bonded electron pairs).
London Dispersion Forces
The temporary instantaneous dipole formed due to the rapid and random motion of electrons.
Dipole-Dipole Forces
An intermolecular force between two polar molecules that have permanent dipoles. Attractive forces exist between the positive end of one polar molecule and the negative end of another polar molecule.
Hydrogen bonding
The intermolecular attraction between two molecules which both contain a hydrogen bonded to a highly electronegative element such as oxygen (O), fluorine (F), or nitrogen (N).
Chromatography
Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis.
Resonance Structure/hybrid
resonance hybrid:
An intermediate form of a molecule which exists when more than one valid Lewis formula can be drawn.
Resonance is a way of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by a single Lewis formula.
A molecule or ion with such delocalized electrons is represented by several contributing structures (also called resonance structures or canonical forms).
Expanded octet
The ability of a central atom from period 3 or below to achieve stability with more than 8 electrons in its outer shell. For example, Xe, P, or S.
Molecular Geometry
The three-dimensional arrangement of the atoms in a molecule, determined using VSEPR theory.
Formal charge
The theoretical charge of an entire molecule based on the electron distribution of the atoms within the molecule.
Sigma and pi bonds
Sigma bond:
A bond formed when atomic orbitals overlap head-on and the electron density is concentrated along the bond axis.
Pi bond:
A bond formed when one atomic orbital overlaps sideways with another atomic orbital, with electron density concentrated on opposite sides of the bond axis
Hybridization (sp3, sp2, sp)
The process by which atomic orbitals within an atom mix to produce hybrid orbitals of intermediate energy.
sp3: A form of hybridization that involves 1 s-orbital and 3 p-orbitals.
sp2: A form of hybridization that involves 1 s-orbital and 2 p-orbitals.
sp: A form of hybridization that involves 1 s-orbital and 1 p-orbital.
electron domain (Geometry)
Electron domain:
The region in which bonding and non-bonding pairs of electrons are most likely to be found. Non-bonding pairs, single bonds, double bonds and triple bonds each count as one electron domain.
Electron domain geometry:
The shape of the arrangement of electron domains surrounding a central atom in a molecule or ion
