#1: Structure Determines Properties Flashcards
Atomic Number
Number of protons in the nucleus of a specific atom.
Wave Functions
The solutions to arithmetic expressions that express the energy of an electron in an atom.
Orbital
Strictly speaking, a wave function. It is convenient however, to think of an orbital in terms of the probability of finding an electron at some point relative to the nucleus, as the volume inside the boundary surface of an atom, or the region in space where the probability of finding an electron is high.
Principal Quantum Number
The quantum number (n) of an electron that describes its energy level. An electron with n=1 must be an s electron; one with n=2 has s and p states available.
Shell
The group of orbitals that have the same principal quantum number n.
Boundary Surfaces
The surface that encloses the region where the probability of finding an electron is high (90-95%).
Spin
Synonymous with spin quantum number.
Spin Quantum Number
One of the four quantum numbers that describe an electron. Can have a value of either +0.5 or -0.5.
Pauli Exclusion Principle
No electrons can have the same set of four quantum numbers. An equivalent expression is that only two electrons can occupy the same orbital, and then only when they have opposite spins.
Nodal Surfaces
A plane drawn through an orbital where the algebraic sign of a wave function changes. The probability of finding an electron at a node is 0.
Hund’s Rule
When two orbitals are of equal energy, they are populated by electrons so that each is half-filled before either one is doubly occupied.
Valence Elctrons
Outermost electrons, the ones most likely to be involved in chemical bonding and reactions. Maximum number of electrons in a valance shell is 8.
Noble Gases
Or rare gases. Characterized by an extremely stable “closed-shell” electron configuration and are very unreactive. Full valance shell. Group 8A elements.
Compounds
An assembly of two or more atoms with properties different from the individual atoms.
Chemical Bond
Attractive force between atoms in a compound.
Ionic Bond
Force of attraction between oppositely charged species (ions).
Very common in inorganic compounds, but rare in organic compounds.
Cations
Positively charged ions.
Anions
Negatively charged ions.
Ionization Energy
Large amount of energy that must be transferred to any atom to dislodge an electron.
In general, ionization energy increases across a row in the periodic table.
Endothermic
Term describing a process or reaction that absorbs heat. Energy has a + sign.
Exothermic
Term describing a reaction or process that gives off heat. Energy change has a - sign.
Election Affinity
Energy change for addition of an electron to an atom.
Energy change associated with the capture of an electron by an atom.
Electrostatic Attractions
Or coulombic attractions. Attractive forces between two oppositely charged particles.
Covalent Bond
Chemical Bond between two atoms that results from their sharing of two electrons.