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periodic trends
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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