Chapter 6 Periodicity
Obj. 1…Periodic Law • Elements on the periodic table (PT) are organized by their physical and chemical properties. • Periodic Law states that the phys. and chem. props. of elements are a ‘periodic function of their atomic #’. (p+) • As elements are placed in order of atomic #, patterns of properties start to develop.
Obj. 2…Organization of the PT • PT is based on work done by Mendeleev and Moseley. • Both arranged elements in rows and columns. • Mendeleev – according to atomic mass. • Moseley – according to atomic #s (**modern PT**).
Obj. 2 cont… • Horizontal rows = periods = energy level • Vertical columns = groups or families = valence e-. • groups are represented by… - single # (1-18) - roman numeral and letter (A or B)
Obj. 2 cont… • ‘A’ groups = representative elements (s and p orbitals) - group # = valence e-. • ‘B’ groups = transition metals (d orbitals) - 2 valence e- (‘s’ orbital) • ‘Lanthanide’ & ‘Actinide’ series = f orbitals - no group #
Obj. 3…Location of Groups NON-METALS METALLOIDS METALS METALS • Metalloids touch the zig-zag! • Metals are to the left of the zig-zag. • Non-metals are to the right of the zig-zag. (+ H)
Obj. 3 cont… REPRESENTATIVE ELEMENTS NOBLE GASES HALOGENS ALKALINE EARTH ALKALI METALS TRANSITION METALS RARE EARTH METALS LANTHANIDE ACTINIDE • Alkali Metals = group 1A (Li – Fr) • Alkaline Earth Metals = group 2A (Be – Ra) • Actinide Series = orbital 5f (Th – Lr) • Representative Elements = ‘A’ groups = S & P orbitals • Noble Gases = group 8A (He – Rn) • Rare Earth Metals = Lanthanide Series (Ce – Lu) • Lanthanide Series = orbital 4f (Ce – Lu) • Halogens = group 7A (F – At) • Transition Metals = ‘B’ groups or ‘d’ orbitals
Obj. 4…Octet Rule • valence e- are all e- in the ‘s’ and ‘p’ orbitals on the highest energy level. • ‘s’ orbitals hold 2 e-. • ‘p’ orbitals hold 6 e-. • max. of 8 valence e- for any element! • all Noble Gases (8A) (except He) have 8 valence e-. - very stable!!! (happy ) • all other elements on the PT want to be like group 8A! - 8 valence e-
Obj. 4 cont… • to get 8 valence e-… • metals (left side of PT) tend to lose e-. • non-metals (right side of PT) tend to gain e-. • METALS… Magnesium (Z = 12): two options: - gain 6 e- oxidation # - lose 2 e- ** +2 charge - 12 p+ and 10 e- = - (+) ion = cation
Obj. 4 cont… • NON - METALS… Chlorine (Z = 17): two options: - gain 1 e- ** oxidation # - lose 7 e- -1 charge - 17 p+ and 18 e- = - (-) ion = anion *Halogens are the most reactive elements.
Obj. 4 cont… • group by group… IAIIAB GroupsIIIAIVAVAVIAVIIAVIIIA lose 2 e- gain 1 e- lose 1 e- lose 2 e- gain 3 e- gain 2 e- lose 3 e- lose or gain 4 e- N/A + 3 +/- 4 - 3 - 2 - 1 + 2 + 2 0 + 1
Obj. 5…Outer e- Configuration • practice… • who is… 6s2 6p5 Astatine (At) Francium (Fr) 7s1 5s2 Strontium (Sr) Tungsten (W) 6s2 5d4 5s2 4d5 Technetium (Tc) Arsenic (As) 4s2 4p3 3s2 3p6 Argon (Ar) Krypton (Kr) 4s2 4p6
Obj. 6 - 7…Vocab. and Trends • ionization energy: energy needed to steal a valence e- from a neutral atom. • increases as you move across a period. - harder to steal from non-metals than metals • increases as you move a group. - harder to steal from small atoms than large - e- are closer to the nucleus in small atoms. ** Helium (He) has highest!
Obj. 6-7 cont… • electronegativity: ability of an atom to attract e-. • increases as you move across a period. - non-metals need to gain e- to be stable. • increases as you move a group. - small atoms attract e- easier b/c nucleus is close to e- it is trying to steal! ** Fluorine (F) has highest!
Obj. 6-7 cont… • atomic radius: distance from nucleus to valence e-. • increases as you move a group. - more energy levels = larger radius. • increases as you move across a period. - less e- = less attraction to nucleus. - ‘fluffy’ - more e- = tighter atom. ** Francium (Fr) is biggest!
Obj. 6-7 cont… • ionic radius: radius of an atom after it gains/loses e-. • increases as you move a group. - more energy levels = larger radius. (metals: + ions) CATIONS: - lose e-, so cation is smaller than neutral atom. (non-metals: - ions) ANIONS: - gain e-, so anion is larger than neutral atom.
Obj. 6-7 cont… • metallic character: ability of an atom to lose e-. • increases as you move across a period. - metals need to lose e- to be stable. • increases as you move a group. - larger atom = easier to lose e-. - less attraction b/n nucleus and valence e-. ** Francium (Fr) is most active!
Obj. 6-7 cont… • non-metallic character: ability of an atom to gain e-. • increases as you move across a period. - non-metals need to gain e- to be stable. • increases as you move a group. - smaller atom = easier to gain e-. - more attraction b/n nucleus and valence e- of neighbor atom. ** Fluorine (F) is most active!
Obj. 6-7 cont… • ionization energy: • electronegativity: • atomic radius: • ionic radius: cation = smaller / anion = larger • metallic character: • non-metallic character:
Obj. 6-7 cont… • Oxidation #... See Objective 4 (Octet Rule) • Outer e- configuration... See Objective 5
Chapter 7 • 92 natural elements (all after U man-made) • * Groups 1A-8A = Representative Elements • * elements in a 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
Chapter 7 • “S” block elements • Hydrogen (hydro = water + genes = to form) • * 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 all H • deuterium- mass of 2, 1 neutron, • “heavy water” used in nuclear reactors • tritium – mass of 3, radioactive, rare
Chapter 7 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
Chapter 7 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 Be Mg Ca Sr Ba Ra
Chapter 7 “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 B Al Ga In, Tl
Chapter 7 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 4 allotropes (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
Chapter 7 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 As Sb Bi may lose 3 e- [Xe]6s24f145d106p3
Chapter 7 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 Se Te Po
Chapter 7 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” F Cl Br I At H
Chapter 7 8A: Noble Gases * 8 e- in outer shell ( fulls2p6anoctet - very stable) * found in free state, until 1962 no cmpds known used to be called inert gases b/c didn’t react He Ne Ar Kr Xe
Chapter 7 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: Fe Cu Co Cr Zn