Read Section 3.8 before viewing the slide show.

Unit 13 Electrons and their Relationship to the Periodic Table Basic Periodic Table Nomenclature Identify Valence Electrons from the Periodic Table Identify Named Groupings of Elements on the Periodic Table

Basic Periodic Table Nomenclature Rows are called periods. Periods are numbered from 1 at the top to 7. Columns are called groups or families. The currently adopted numbering system is to start with 1 at the first group on the left and number through 18 on the right. Older systems are still used that place Roman numerals at the top of each group, but we will stick with the newer version.

Electron Configurations from the Periodic Table Period Number: Electron Configurations from the Periodic Table Group Numbers 1 2 3 4 5 6 7

Electron Configurations Related to Periodic Table Electron configurations for elements in the same group have some similarity – the shell number increases by 1 for each row down the periodic table and the outer electrons are in the same subshell. For example, consider the first four elements of Group 1: Notice how each electron configuration ends in ns1 where n is the shell number. The electrons in the highest numbered shell are called the valence electrons. All elements in the same group have the same number of valence electrons – in this case 1 valence electron. Element # electrons Electron Configuration H 1 1s1 Li 3 1s22s1 Na 11 1s22s22p63s1 K 19 1s22s22p63s23p64s1

Valence Electrons and Group Number Because of the relationship between electron configuration and group number, members of the same group have the same number of valence electrons. The number of valence electrons in a group is equal to the last digit in the group number. For example: Phosphorous (Z=15) is in Group 15 and has 5 valence electrons Strontium (Z=38) is in Group 2 and has 2 valence electrons Gallium (Z=31) is in Group 3 and has 3 valence electrons The above rule applies well for elements in Groups 1-2 and 13-18. The others become a little more problematic.

Named Regions of the Periodic Chart As may be expected, over time names have been assigned to regions of the periodic table. Representative or Main Group elements (Groups 1-2 and 13-18, blue border on the chart to the right) Transition Elements (Groups 3 – 12, red on the chart above) Inner Transition Elements (Below the main framework of the chart, green on the chart above)

More Named Regions Some groups are given special names as well. Remember that elements in the same group have similar properties so it is reasonable to name groups for easy reference Alkali Metals – Group 1 (blue on this chart) Alkaline Earth Metals – Group 2 (red on this chart) Chalcogens – Group 16 (green on this chart) Halogens – Group 17 (yellow on this chart) Noble gases – Group 18 (orange on this chart)

Metals and Nonmetals One more important classification is metals and nonmetals. We will make decisions about types of compounds, formula writing, and nomenclature based to a large extent on this criterion. Metals – those elements to the left of the stair-stepped line indicated on the chart to the right Nonmetals - those elements to the right of the stair-stepped line (blue on the above chart) indicated on the chart above Metals tend to conduct electricity and heat well, are malleable (can be shaped by pounding), and are ductile (can be drawn). Nonmetals typically do not have these properties.

The End