Chemical Periodicity Chapter 6

Trends in the periodic table Understand general trends in the periodic table between –atomic radii (and ionic radii) –ionization energy –electron affinity –electronegativity.

Atomic radius The “bonding atomic radius” – ½ distance between two identical atoms Coulombic law of attraction

Properties affecting atomic radius 1.orbital size: –What will happen to the radius as number of orbital shells increases?

effective nuclear charge Shielding effect of core electrons (S) Nuclear effective charge, Z eff Z eff = Z – S –What is Z? What is S? What happens to Z eff as we go from left to right along the table? How does this affect the radius?

Isoelectronic series series of atoms and ions containing the same number of electrons. Size is directly proportional to charge

Ionization energy: the energy required to remove one electron from an atom what do you think will happen with the ionization energy, based on what you have learned about atomic radius?

Both the atomic radius and the type of orbital affect IE

removing more than one electron removing valence electrons vs. removing core electrons Ionization Energies in kJ/mol H1312 He Li Be B C N O F Ne Na Mg

Electron affinity the energy change that occurs when an electron is added to an atom (forming an anion)

Electronegativity Electronegativity: How does this differ from electron affinity? General trend:

Alkali metals (column 1A) Always form +1 ions electron configuration: very reactive in water M + H2O  MOH (M = Li, Na, K, Rb, Cs)

Alkaline earth metals (2A) Always forms +2 ions electron configuration: Be, Mg not reactive in liquid water

Nonmetal groups Chalcogens (6A) usually form –2 ions electron configuration: Halogens (7A) usually form –1 ions electron configuration: Noble gases (8A) do not form ions electronic configuration usually unreactive, but heavier atoms (Kr, Xe, Rn) do form compounds.

Hydrogen and the hydrides The text has grouped various reactions according to those with hydrogen and oxygen. Many of the trends we have examined are also discussed there.

Metal hydrides In general: xM(l) + H 2 (g) → xMH (s) Where M is a IA or IIA metal. What is x if M is –IA? –IIA?

Hydrides and hydroxides Metal hydrides react with water to form metal hydroxides. Because of this, they are __________. The general form is MH x (s) + xH 2 O (l) → M(OH) x (s) + xH 2 (g) Again, what is x for –alkali metals? –alkaline earths?

Molecular hydrides Halogens react with hydrogen…. H 2 (g) + X 2 (g)→ 2HX (g) These are molecular compounds. But what happens to HCl when dissolved in water? Hydrogen halides are ________.

Metals and oxygen Oxygen has three kinds of ions: Oxide: Peroxide: Superoxide:

Metal oxides in water Basic anhydrides: A basic anhydride is similar to a metal hydroxide base, but without _______. Soluble metal oxides react with water to form _____ __________ __________.

Molecular oxides Nonmetal reacting with water form molecular oxides. These reactions are more complex; we will discuss them later in the semester. However, just like molecular hydrides, molecular oxides tend to be ___________.

combustion There are examples of complete combustion and incomplete combustion of hydrocarbons in your text. You should be familiar with these. (p 258) Complete combustion of a hydrocarbon (contains only C, H, O) will always form ____________________ as products.