1. Chemistry Chapter 6/7 Notes #2 LaVigne

2. Classification of Elements H: 1s 1 Li [He]2s 1 Na [Ne]3s 1 K [Ar]4s 1 Be: [He]2s 2 Mg [Ne]3s 2 Ca [Ar]4s 2 Sr [Kr]5s 2 What do elements in the same groups have in common with one another? Same number of valence electrons (electrons in the outermost energy level)

3. Classification of Elements Elements in the same group have similar chemical properties because they have the same number of valence electrons The energy level of an element’s valence electrons indicated the period on the periodic table that it is found in. Representative elements - # of valence electrons are also related to group number Periodic Table

4. Slide 3: classification of elementsSlide 3: classification of elements Slide 9: “noble gases”Slide 9: “noble gases” Slide 6: Alkali metalsSlide 11: Other metals

5. Valance Electrons Electrons in the outermost energy level (highest s and p sublevels) Ex. Mg Ex. Br Columns on the periodic Table (1-8)

6. Electron Dot Structures Shows the number of valence electrons (electrons in the outermost energy level) of an atom Write the chemical symbol – put dots around it ElementGroupe - dot Magnesium2 Fluorine7 Nitrogen5 Carbon4

7. Classification of Elements- Blocks s-Blocks: Groups 1 and 2 The alkali and alkaline earth metals Different numbers of nonvalence e- result in different properties Periodic Table Hydrogen (an exception) 1A, 1 ve-, but halogen props. Can gain or lose one electron Gaining makes it act like a nonmetal Losing makes it act like a metal Can be created by electrolysis of water or adding a metal to an acid

8. Alkali metals Group 1 – one valence electron Can lose a valence electron, gets a +1 charge (oxidation state) Soft and shiny metals Soft enough to cut with a knife Very reactive – so they are mostly found as compounds in nature Violently reacts with water (it gets stored in oil so it doesn’t react with water vapor in the air) More reactive as you move down the column Periodic Table

9. Alkaline Earth Metals Group 2 – 2 valence electrons Can lose 2 e- and can have a +2 charge (oxidation state) Shiny solids, harder than alkali’s Earth’s – didn’t melt in fire Do not dissolve in water very well Also very reactive Not as reactive as alkali metals Found as compounds most of the time More reactive as you move down the column

10. Classification of Elements- Blocks p- block: groups 3-8 Different numbers of non-valence e- result in different properties in each column Periodic Table Group 3 – 3 v.e- Commonly Oxide compounds Group 4 – 4 v.e- C = unlike other elements in its group Graphite, diamond (allotropes – same element, different structures, different properties) Carbon Chem= organic

11. More p-block Elements Group 5 – 5 V.e- N- used in ammonia Bacteria can turn env. N into a form plants & animals use Group 6 – 6 V.e- O = most abundant element in Earth’s Crust Is ozone (O 3 ) Other Metals = Poor metals Other nonmetals Important (for living things Oxygen, Nitrogen, Sulfur, Carbon Periodic Table

12. Halogens Group 7 – 7 valence electrons Tend to gain an e- to get full outer shell Results in a -1 charge (oxidation state) Very reactive gases Fluorine is the most reactive element Mostly found as compounds Chorine is found in many cleaning compounds (bleach, etc) Halogen means “salt former” Tend to form compounds referred to as salts (NaCl, MgCl 2, etc) Exception = astinine – radioactive, no known uses

13. Noble Gases Group 8 – 8 valence electrons Full outer energy level of electrons (octet rule) Inert (non-reactive) colorless Exist as single atoms Periodic Table Helium is the exception to the rule Only has only s- sublevel e- (it only has 2) But is full, and shares properties with the noble gases

14. Classification of Elements- Blocks d- block: Transition Elements Conductors, malleable, ductile, lustrous Hard with high m.p. And b.p. The more unpaired e- in d sublevel, the higher the mp and bp are, + are harder Little variation in size and reactivities Can form atoms with varying charge (multiple oxidation states) Unpaired d e- can also be lost A change in charge can be detected by a color change

15. Classification of Elements- Blocks f-block: Inner transition Elements (periodic table)periodic table Lanthanides – silvery metals with high melting points Actinides – Radioactive 3 exist in nature (Th, Pa, and U) – the rest are synthetic All decay very quickly (except plutonium – so it is often used in nuclear reactors)

16. Slide 5: s-blocks slide Slide 8: “p-block” Slide 15: “f-block”