152 1-31-2011

gs, es, impossible states – look at QN’s

• For electrons in C• Ground state• 1s2 2s2 2p2 __ __ ___ ___ ___• Excited state• 1s2 2s1 2p3 __ __ ___ ___ ___• Impossible• 1s3 2s3 ___ ___ or 1s2 1p4 ___ ___ ___ ___• We can violate Hund’s rule and aufbau – but NOT

Pauli • Blue violates the QN rules 1 p would have l = to n

and l must be 1 less than n

Order of filling puts the 4s electrons in first --- but energy wise 4 level is higher than 3 level

Periodic trends

• Size – atomic radius– ENC (effective nuclear charge)

• Charge felt by outer electrons

– Across table Increases– Down table decreases

• Size – Ionic radius

• Cations are smaller than atoms– Larger charge, smaller ion (within period)

• Anions are larger than ions– Larger charge, slightly larger (within period)

• http://www.mpcfaculty.net/ron_rinehart/periodic.htm

• IE (ionization energy)– Energy required to remove highest energy (most

outer) electron from atom (1st IE)– Increases across table (ENF)– Decreases table (size, decreased electrostatic

attraction)

Electron affinity

• The Electron affinity of a molecule or atom is the energy change when an electron is added to the neutral atom to form a negative ion. This property can only be measured in an atom in gaseous state.

• X + e− → X−

The Electron affinity of a molecule or atom is the energy change when an electron is added to the neutral atom to form a negative ion. This property can only be measured in an atom in gaseous state.X + e− → X−

The Electron affinity of a molecule or atom is the energy change when an electron is added to the neutral atom to form a negative ion. This property can only be measured in an atom in gaseous state.X + e− → X−

kJ/mol* ~ 0

X + e- X- EEA = Einitial - Efinal (backwards!!!) or energy release when electron addedOr amount of energy to remove e- from singly charged ionNon-metals release significant energy when e- added to neutral atom, or significant energy is Required to removed electron from negative non-metal ions

http://gohs.tvusd.k12.ca.us/TeacherWebs/Science/itaylor/Global/WS/Electronegativity%20chart.pdf

# 53-60

Electronegativity – rates the ability of a atom to attract electronsMore user friendly than electron affinity

Summary of trends