Electron Configuration and Valence Electrons Chp 5.3

The arrangement of electrons in an any atom is called the atom's electron configuration. 3 rules define how electrons can be arranged in atomic orbitals.

The Hog Hilton aka the atom Hotel floors = Rooms = Pigs = Aufbau principle-electrons enter lowest Energy level first Hog Rules- Pauli exclusion principle-orbitals hold at the most 2 electrons with opposite spins Hund’s rule-Electrons occupy the same Energy level with parallel spins ( ), then opposite spinning electrons fill the orbitals. ( )

The Hog Hilton aka the atom Hotel floors = energy levels Rooms = orbitals Pigs = electrons Aufbau principle-electrons enter lowest Energy level first Hog Rules-Hogs are very scared of heights Pauli exclusion principle-orbitals hold at the most 2 electrons with opposite spins Hog Rules-Hogs stink, no more than 2 per room Hund’s rule-Electrons occupy the same Energy level with parallel spins ( ), then opposite spinning electrons fill the orbitals. ( ). Hog Rules- Hogs face opposite directions when rooming together

The Hog Hilton aka the atom Hotel floors = energy levels Rooms = orbitals Pigs = electrons Carbon = 6 electrons (hogs) Aufbau principle-electrons enter lowest Energy level first Hog Rules-Hogs are very scared of heights Pauli exclusion principle-orbitals hold at the most 2 electrons with opposite spins Hog Rules-Hogs stink, no more than 2 per room Hund’s rule-Electrons occupy the same Energy level with parallel spins ( ), then opposite spinning electrons fill the orbitals. ( ). Hog Rules- Hogs face opposite directions when rooming together

Read the PT left to right S orbital P orbital Read the PT left to right Write the energy level number first, then the orbital letter, then how many electrons are contained as a superscript. Carbon: d orbital Energy level subtracts by 1. Energy levels are vertical on the PT. 1-7 f orbital Energy level subtracts by 2

The Shortcut-Noble Gas Configuration Find the noble gas that comes “before” the element on the periodic table. Use this noble gas in brackets at the beginning and continue on until you reach the element.

There are exceptions to predicted configurations There are exceptions to predicted configurations. After element 23 some configurations are written differently because half-filled and filled sets of s and d orbitals are more stable. The electron is borrowed from the 4s orbital to achieve more stable (unreactive) configuration (half filled or all filled d orbitals). Others: Mo, Ru, Rh, Pd, and Ag

Valence Electrons: electrons in the atom's outermost orbitals-generally those with the highest principal energy level. Only valence electrons determine the chemical properties of an element

Electron Dot Structure Because valence electrons are involved in forming chemical bonds, chemists often use a shorthand method, called electron dot structure. This consists of an element symbol and dots representing all of the atom's valence electrons.