Chpt7 - Chapter 7 Periodic Properties of the Elements...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter 7 Periodic Properties of the Elements Development of Periodic Table • Elements in the same group generally have similar chemical properties. • Properties are not identical, however. Development of Periodic Table Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped. Development of Periodic Table Mendeleev, for instance, predicted the discovery of germanium (which he called eka- silicon) as an element with an atomic weight between that of zinc and arsenic, but with chemical properties similar to those of silicon. Periodic Trends • In this chapter, we will rationalize observed trends in – Sizes of atoms and ions. – Ionization energy. – Electron affinity. Effective Nuclear Charge • In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons. • The nuclear charge that an electron experiences depends on both factors. Effective Nuclear Charge The effective nuclear charge, Z eff , is found this way: Z eff = Z − S where Z is the atomic number and S is a screening constant, usually close to the number of inner electrons. Effective Nuclear Charge • Screening explains why orbitals with higher I in a given shell have higher energies. • Z eff increases in moving from left to right across a period • Number of core electrons remains constant, the number of protons increases, and valence electrons that are added are poor at screening the charge • Z eff also increases in moving down a group but much less dramatically. Larger electron cores screen less effectively. Sizes of Atoms • The nonbonding atomic radius (van der Waals radius) is the effective radius of an atom when it is not bonded to another atom. • The bonding atomic radius (covalent radii) is defined as one-half of the distance between bonded atoms. Sizes of Atoms Bonding atomic radii tend to… …decrease from left to right across a row due to increasing Z eff . …increase from top to bottom of a column due to increasing value of n Sizes of Ions • Ionic radii are based on the distances between ions in ionic compounds. • size depends upon: – Nuclear charge....
View Full Document

This note was uploaded on 04/25/2008 for the course CHEM 131 taught by Professor Sykora during the Spring '08 term at S. Alabama.

Page1 / 52

Chpt7 - Chapter 7 Periodic Properties of the Elements...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online