Module 2.5 General Chemistry 1 w Lab
Objectives
- Explain and apply observed trends in atomic size, ionization energy, and electron affinity of the elements
Periodic Variations in Element Properties
- Why do elements in periodic table exhibit similar chemical behavior?
- Because members of a group have the same number and distribution of e- in their valence shells
- A period is a horizontal row of the periodic table. A group is a vertical row of the periodic table
- Even though valence electrons stay the same, the principle quantum number increases by one
- Because members of a group have the same number and distribution of e- in their valence shells
- What are other patterns in the periodic table?
- Moving down a group
- Metallic character of atoms increases
- Elements become more solid
- Left to right
- Add proton to nucleus + electron to valence shell
- Moving down a group
- What 3 properties vary periodically as electron structures and elements change
- Size
- Ionization E
- Electron affinities
Variation in Covalent Radius
- How to determine relative size of an atom?
- Covalent radius
- Defined as half distance between nuclei of 2 identical atoms joined by covalent bond
- Covalent radius
- What happens when the principle quantum number increases by one for each element?
- electrons are being added to a region of space increasingly distant from the nucleus
- Atom size and covalent radius must increase as we increase distance of outermost electrons from the nucleus
Terminology