Chapter 4 – The Periodic Table Developed by Mendeleev His work led to the Periodic Law which states that chemical and physical properties of the elements are periodic functions of their atomic number

General Analysis of the Periodic Table Each row is called a period Elements are arranged in order of increasing Z (atomic number) Each column is called a group or family Plays a significant part in predicting properties of elements There are 18 columns The MAIN GROUPS are the first two groups and groups 13 to 18

The periodic table is arranged by electron structure (according to valence electrons) since they determine chemical properties

Periods Not much significance but some characteristics to note: In general,the number of the period is the same number of the energy level where the valence e- are found Example: oxygen Found in the 2 nd period so its valence e- are located in the 2 nd energy level

Short Periods Periods 1, 2, and 3 Period 1 elements hold only a maximum of 2e - Periods 2 and 3 elements hold a maximum of 8 e -’ s

Fourth and fifth periods Are long periods as they contain 18 elements Contain elements with electrons in the d- orbital The elements in the d-block are called transition metals They form positive ions which have incomplete d-orbitals

Sixth & Seventh Periods 6 th period contains 32 elements 7 th period contains space for 32 elements-but only 23 are known A section has been “removed” and placed on the bottom The top period is called the “lanthanides” – all contain e-’s in the 4f-orbital The bottom period is called the “actinides” and all elements contain e-’s in the 5f orbital

Other features on the Periodic Table A) Metals Make up the largest portion have luster, ductile and malleable conduct electricity High melting and boiling points

B) non-metals Non-conductors of electricity Low boiling point Can be solid, liquid or gas Non-lustrous

c) Metalloids Semi-conductors Have properties of both a metal and non- metal