3.1-3.3 The Periodic Table, Orbital Energies, Electron Configurations and Orbital Diagrams

periodic properties of the elements

predictable properties based on an element’s position (row and column)

which energy orbits get occupied by electrons first?

the lowest energy orbitals available

ground state

when all electrons are in the lowest energy orbitals possible

excited state

some electron(s) are in higher energy orbitals

in hydrogen atoms, the sublevels are _____

degenerate (of equal energy) (3s=3p=3d)

in multi-electron atoms, the energy of an electron depends on both the values of ___ and ___(principal level and sublevel)

n and l
(for given value of n: s<p<d<f

Coulomb’s Law

gives the potential energy between 2 charged particles (q1 and q2)

E(+) repulsion

increases energy of a system…destabilizing effect

E(-) attraction

decreases energy of a system…stabilizing effect…energetically favorable

|E| potential energy between 2 charges

is proportional to magnitude of charges and inversely proportional to the distance between the charged particles

2 orbital effects that impact electron energies

shielding and orbital penetration

the closer the electron to the nucleus, the ____ energy it has

LESS

less energy =

CALMER AND STABLE ATOM!

shielding

when electrons in energy levels with larger values of n do not “feel” the full effects of the nucleus because of the charge shielding from inner electrons (they feel a weaker net positive charge)

orbital penetration

the ability of an electron in a specific orbital to get physically close to the nucleus by slipping past the electron density of inner-shell (core) electrons

order of orbital penetration

ns > np > nd > nf…
so s-orbital electron is CLOSER to nucleus —> LOWER, MORE STABLE ENERGY

orbital diagram

a visual tool that shows how electrons are organized inside an atom's energy levels (boxes with arrows inside)

up down half arrows

represent electron spin (m_s=+1/2 or -1/2)

Aufbau Principle

lowest energy orbitals are filled first

Hund’s Rule

when filling individual orbitals of a given sublevel, electrons fill them singly first with parallel spins

2 electrons sharing an orbital MUST have _______ spins

OPPOSITE

Pauli exclusion principle

no 2 electrons in an atom can have the same 4 quantum numbers

Electron Configurations

the arrangement of electrons in the energy levels, subshells, and orbitals of an atom