Chapter 5, Section 3
Electron Configuration and Periodic Properties
- The atomic radius may be defined as one-half the distance between the nuclei of identical atoms that are bonded together.
- The trend to smaller atoms across a period is caused by the increasing positive charge of the nucleus.
- In general, the atomic radii of the main-group elements increase down a group.
- A negative ion is known as an anion.
- Metals at the left tend to form cations and the nonmetals at the upper right tend to form anions.
- Cationic radii decrease across a period because the electron cloud shrinks due to the increasing nuclear charge acting on the electrons in the same main energy idea.
-Outer electrons in both cations and anions are in higher energy levels as one reads down a group.
- Valance electrons are most commonly found in incompletely filled main-energy levels.
Periodic Properties of the d- and f-Block Elements
- d-block elements generally decrease across the periods.
- the decrease is less than that for the main-group elements because of the extra electrons in the sublevel.
-The f-block elements are located between lanthanum and hafnium.
-There is a great increase in atomic number when you hit the f-block elements.
- The energy in both blocks increase across the periods.
- This happens because there are electrons available for ionization in the outer s sublevels are less shielded from the increasing nuclear charge by electrons in the incomplete sublevels.
Ion Formation and Ionic Radii
- electrons in the highest occupied sublevel are always removed first.
- THis means that although newly added electrons occupy the d-sublevels.
-The d-block elements also follow the general trend for electronegativity values to increase as radii decrease, and vice versa.
- The f-block elements all have similar electronegativities.