Transcript Electron Configurations and Periodic Properties

Electron Configurations and
Periodic Properties
5.3
Atomic Radii
• Atomic radius – ½ the distance between
the nuclei of identical atoms that are
bonded together.
• Can be difficult to measure
Atomic Radius
• Trend:
• Decreases across a period
–b/c effective nuclear charge
• Increases down a group
–more E levels / electron shielding
Atomic Radii
Ionization Energy
• You can remove an e- from an atom if
enough E is supplied
• A + energy = A+ + e• The A+ is an ion of that atom w/ +1
charge
Ionization Energy
• Ion – atom or group of bonded atoms
that has a + or – charge
• Ionization – any process that results in
the formation of an ion
• Ionization energy – the E required to
remove 1 e- from a neutral atom of an
element (aka First Ionization Energy IE1
Ionization Energy
Ionization Energy
• The Trend
–Increase across a period
• B/c increase effective nuclear
charge
–Decrease going down the group
• e- further out – electron shielding
Removing e- from + ions
• If enough E is supplied, you can remove
more e• Called second ionization E, or third
ionization E, & so on
• 2nd and 3rd are always higher than
previous b/c effective nuclear charge
Electron Affinity
• Electron Affinity – the E change that
occurs when an e- is acquired by a
neutral atom
• Some give off E = A + e-  A- + E
• Some require E = A + e- + E = A–These are unstable and hard to determine
Electron Affinity
• Trend:
• Increases across a pd (except nob. gas)
–Increasing nuclear charge
• Decreases down a group
–Increase in e- shielding b/c larger atomic
radius
Electron Affinity
• 2nd e- affinities are always more
positive (requires more E) than 1st eaffinities
Ionic Radii
• Cation – a positive ion
–Made from the loss of an e–Creates smaller radii
• Anion – a negative ion
–Addition of 1 or more e–Creates a larger radii
Ionic Radii
• Trend …
• Cationic and anionic radii decrease
across a pd
–B/c increasing nuclear charge
• Both increase down a group
Ionic Radii
Valence Electrons
• V.E. – e- available to be lost, gained,
or shared in the formation of
chemical compounds
• Located in incompletely filled main-E
levels
• For MGE – located in outermost s&p
Electronegativity
• e-neg – a measure of the ability of an
atom in a chemical compound to attract
e- from another atom in the cmpd.
• Trend… (NOBLE GASES EXEMPT)
• Increase across pd.
• Decrease down a group
Electronegativity
Properties of the d and f block
• Not as straight forward as the others
• e- fill in lower E levels for these
blocks so some differences occur
• Some E levels promote or demote eto obtain more stability (4s13d5)