Periodic Properties of the Elements Chapter 7
The Sizes of Atoms The bond distance: d The covalent radius of the atom Non-bonding atomic radius
Atomic size varies consistently through the periodic table.
Atomic size varies consistently through the periodic table.
The larger ionization energy, the more difficult it is to remove the electron. Ionization Energy Ionization energy: the minimum energy (kj/mol) required to remove an electron from the ground state of a gaseous atom or ion. The first ionization energy(i 1 ): Na (g) Na + (g) + e - The second ionization energy(i 2 ): Na + (g) Na 2+ (g) + e - I 1 < I 2 < I 3 The third ionization energy(i 3 ): Na 2+ (g) Na 3+ (g) + e-
Periodic Trends in Ionization Energy
Filled n=1 shell Filled n=2 shell Filled n=3 shell Filled n=4 shell Filled n=5 shell
Electron Affinities Electron Affinity: the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion. X (g) + e - X - (g) F (g) + e - F - (g) O (g) + e - O - (g) EA = -328 kj/mol EA = -141 kj/mol
Electron Affinities Electron affinities Ionization Energy Atom(g) + e - Ion(g) E electron affinity Atom (g) Ion (g) + e I Ionization energy 1 - Cl(g) + e Exothermic Electron affinities Endothermic Cl (g) - E - Ar(g) + e - + Ar (g) - E -
Electron Affinities The more negative the electron affinity, the greater the attraction of the atom to an electron
Ion Radii
Metals, Nonmetals, and Metalloids
Metals, Nonmetals, and Metalloids Metals Metallic character increases down a group. Metallic character decreases across a period. Metals have low ionization energies. Most neutral metals are oxidized rather than reduced. 2 Cu( s) + O 2 Cu O( s) 2 2 2 Ni( s) + O 2 NiO( s) 2
Metals, Nonmetals, and Metalloids Metals When metals are oxidized they tend to form characteristics cations. All group 1A metals form M + ions. All group 2A metals form M 2+ ions. Most transition metals have variable charges.
Metals, Nonmetals, and Metalloids
Metals, Nonmetals, and Metalloids Nonmetals: Metal + nonmetal salt 2Al(s) + 3Br 2 (l) 2AlBr 3 (s) Metalloids: Metalloids have properties that are intermediate between metals and nonmetals.
Metals, Nonmetals, and Metalloids Metalloids Example: Si (shown here) has a metallic luster but it is brittle. Metalloids have found fame in the semiconductor industry. Sliced thin wafer of large silicon crystals
Metals, Nonmetals, and Metalloids Group 1A: The Alkali Metals + M M + e Reactivity increases as we move down the group 1) Alkali metals + water MOH + hydrogen gas 2 M ( s) + 2 H O( l) 2 MOH( aq) + H ( g) 2 2
Metals, Nonmetals, and Metalloids Group 1A: The Alkali Metals 2) Alkali metal + O 2 different oxides 4Li(s) + O 2 (g) 2Li 2 O(s) (oxide) 2Na(s) + O 2 (g) Na 2 O 2 (s) (peroxide)( ) K(s) + O 2 (g) KO 2 (s) (superoxide)( )
Group Trends for the Active Metals Group 1A: The Alkali Metals Li line: 2p 2s transition Na line (589 nm): 3p 3s transition K line: 4p 4s transition 3) Alkali metals emit characteristic colors when placed in a high temperature flame.
Group Trends for the Active Metals Group 2A: The Alkaline Earth Metals 1) Alkaline earth metals are harder and more dense than the alkali metals. 2 M M + + 2e Mg(s) + Cl 2 (g) MgCl 2 (s) 2Mg(s) + O 2 (g) 2MgO(s) 2) 2 M( s) + 2 H O( l) 2 Be does not react with water. Mg will only react with steam. Ca(s) + 2H 2 O(l) Ca(OH) 2 (aq) + H 2 (g)
Group Trends for Selected Nonmetals Hydrogen 1) To gain another electron to form the hydride ion H : 2Na(s) + H 2 (g) 2NaH(s) 2) To lose its electron to become H + : 2H 2 (g) + O 2 (g) 2H 2 O(g) 3) H + is a proton The aqueous chemistry of hydrogen is dominated by H + (aq).
Group Trends for Selected Nonmetals Group 6A: The Oxygen Group move down the group the metallic character increases O 2 : a gas, Te : a metalloid, Po : a metal Two important forms of oxygen: O 2 and O 3 (ozone) 3O 2 (g) 2O 3 (g) H = +284.6 kj. Ozone: pungent and toxic.
Group Trends for Selected Nonmetals Group 6A: The Oxygen Group Oxygen : a potent oxidizing agent ( O 2- ion : a noble gas configuration) Two oxidation states for oxygen: 2 - (e.g. H 2 O) and 1 - (e.g. H 2 O 2 ) Most common form of sulfur: yellow S 8 Sulfur tends to form S 2- in compounds (sulfides) Ag2 S, CuS, HgS
Group Trends for Selected Nonmetals Group 7A: The Halogens X 2 + 2e - 2X - Fluorine : one of the most reactive substances known 2F 2 (g) + 2H 2 O(l) 4HF(aq) + O 2 (g) H = -758.7 kj. F2, Cl2, Br2, I 2
Group Trends for Selected Nonmetals Group 7A: The Halogens Chlorine: the most industrially useful halogen produced by the electrolysis of brine (NaCl): 2 NaCl( aq) + 2 H O( l) 2 NaOH ( aq) + H ( g) + Cl( g) 2 2 2 2 Cl ( g) + H O( l) = HClaq ( ) + HOCl( aq) hypochlorous acid Disinfects pool water Hydrogen compounds of the halogens are all strong acids with the exception of HF.
Group Trends for Selected Nonmetals Group 8A: The Noble Gases (ns 2 np 6, n 2) 1) Nonmetals and monatomic. 2) Notoriously unreactive (completely filled s and p sub-shells) 3) The first compound of the noble gases was prepared in 1962 : XeF2, XeF4, XeF6 4) To date the only other noble gas compound: KrF 2