* 92 Natural Elements (All After U Man-Made)

Ch 7The Elements

* 92 natural elements (all after U man-made)

* Groups 1A-8A = Representative Elements

* elements in family(group) have same # valence e-

* # & location of valence e- determine chemistry

* metals tend to LOSE e-

metal reactivity increases ↓ a group

and ← a period

* nonmetals tend to GAIN e-

nonmetal reactivity increases ↑ a group

and → a period

“S” block elements

Hydrogen (hydro = water + genes = to form)

The most abundant element in the universe. (He is 2nd)

* 1 valence e- but doesn’t always behave like group 1A

* can lose e- (like metals)

or gain e- (like nonmetal)

* 3 natural isotopes:

protium- mass of 1, 0 neutrons, 99.985% of allH

deuterium- mass of 2, 1 neutron,

“heavy water” used in nuclear reactors

tritium – mass of 3, radioactive, rare

Group 1A: ALKALI METAL

* 1 valence e- ( Na = [Ne]3s1 , K = [Ar]4s1 , Rb = [Kr]5s1 )

* low densities, low melting pts, good conductors,

soft enuf to be cut w/ a knife

* react violently w/ H20 to form H2 gas & metal hydroxide (OH- makes a soln. alkaline or base)

* not usually found in “pure” form, so reactive they are

always forming cmpds, esp like to react w/ halogens

Why?

Rb, Cs, Fr

Group 2A: ALKALINE EARTH METALS

* 2 valence e- ( Be = [He]2s2, Mg = [Ne]3s2, Ca = [Ar]4s2 )

* less reactive than 1A but still make alkaline solns.

react w/acids to form H2 and metallic OH-

* found in mineral ores (earths)

Metal oxides don’t melt in fire, alchemists called them earths

“P” block elements Groups 3A – 8A

3A Boron or Aluminum Family

* most lose 3 valence e- to form 3+ ions B =[He]2s22p1, Al =[Ne]3s23p1

(except Th which loses only 1 “p” e- to form 1+ ion)

* less metallic than group 1 or 2, sometimes will

share e- rather than give 3 away

In, Tl

4A Carbon Group

C nonmetal, Si & Ge metalloids, Sn & Pb metals

* 4 e- in outer shell C = 1s22s22p2 Si = [Ne]3s23p2 Ge = [Ar]4s23d104p2

* 4 is halfway pt of full octet,

could give 4 e- away (metallic)or add 4 e- (nonmetal)

probably will share

C 4allotropes(forms) diamond- nonmetal crystal

Graphite-metalloid, solid lubricant, pencils, tire blacking

Amorphous- coal buckeyball-sphere of C60

Si metalloid, transistors, computer chips, synthetic motor

oils, diodes (lights), lasers

Ge metalloid, both Si and Ge are semiconductors

Meaning: insulators at lo temp, conductor at hi temp

Sn and Pb are metals - not very reactive, good alloys

Pb + Sn = solder, Cu + Sn = bronze

Terms to know:

organic

inorganic

mineral

ore

allotrope

amorphous

5A: Nitrogen Group

N & P nonmetals (gain e-), As & Sb metalloids, Bi metal (lose e-)

* 5 valence e-

N can gain 3e to = 8, 78% of Earth’s atmosphere

P 3 allotropes

Bi may lose 3 e- [Xe]6s24f145d106p3

6A: Oxygen Group

* 6 valence e- O = 1s22s22p4 S = [Ne]3s23p4

O 2 allotropes O2 most abundant element on earth

O3 ozone

S 10 allotropes

7A: Halogens (halos = salt, gen = born)

* 7 valence e-

* most active of nonmetals, usually gain 1 e-

* always found in cmpds, never free

* combines most easily w/ a Group 1 or 2 metal

to form a “salt”

8A: Noble Gases

* 8 e- in outer shell ( fulls2p6 an octet - very stable)

* found in free state, until 1962 no cmpds known

used to be called inert gases b/c didn’t react

Transition Metals “B” groups

* e- going into the d subshell

(full and half full d subshell more stable)

* metallic luster, good conductors, malleable,

many have variable charges

* can form cmpds with nonmetals

* often form alloys w/ other metals

(alloys are mixtures not cmpds)

examples: