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 IE 1

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 2 nd and 3 rd 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 2 nd e- affinities are always more positive (requires more E) than 1 st e- affinities

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 e- to obtain more stability (4s 1 3d 5 )