Groups 1 and 17 of the P.T.

Groups 1 and 17 of the Periodic Table

Reactive Elements,

but for opposite reasons

Key Prior Knowledge

• Valence electrons: electrons in the outermost shell

• Octet Rule: Most elements gain or lose electrons until they have 8 valence e^-

• Ions: particles that have a net electric charge because  $electrons\ne protons$  

• electron configuration: describes organization of electrons into energy levels (last digit is the valence shell)

• Examples:   Na  2-8-1  ;  Cl  2-8-7

Multiple Choice

How many valence electrons does potassium have? (K)

• 1

• 2

• 8

• 19

The Alkali Metals

(Group 1)

• Potassium has 1 valence electron based on its configuration of 2-8-8-1

• Each column of the Periodic Table is a unique Group of elements. (# 1 - 18)

• Atoms of elements in Group 1 all have 1 valence electron.

• This leads to similar chemical properties

• Reactivity increases as you go down the Group

Multiple Choice

Which of these Group 1 Alkali Metals is the most reactive?

• K

• Cs

• Li

• Na

Halogens

(Group 17)

• Name means "salt makers"

• F, Cl, Br, I, At

• Commonly, they have 7 valence electrons. (1 from the octet)

• Reactivity decreases as you go down the Group.

• Steal 1 e- to achieve octet status

Alkali Metals and Halogens often react to form "salt"

• "Salt" is a generic term for an ionic compound involving a halogen

• NaCl

• KBr

• LiF

• NaI

Groups are columns of elements on the Periodic Table and have similar chemical properties

Group 1: Alkali Metals , start with 1 valence e- , highly reactive . (Francium is most reactive metal)

Group 17: Halogens, start with 7 valence e- , highly reactive.

(Fluorine is most reactive nonmetal)

Elements in these Groups tend to react to become ions