24. The four types of periodicity of properties change in the periodic table. Secondary and internal periodicities.

→ Left to right:

 Oxidative and non-metallic properties increase. Example: Li-Be-B-C-N-O-F-Ne

← Right to left:

 Regenerative properties are weakened, and the acid are enhanced. Example: 2K + 2HCl = 2KCl + H2

For example, carbon - nonmetal more pronounced than its neighbor over the period of boron and nitrogen, has an even more vibrant non-metallic properties than carbon.

↓ Top to bottom:

Boosts recovery and metal properties (due to the fact that the lower positioned elements that have already pretty much filled electronic shells) .Electronegativity decreases.

Secondary frequency - it is non-monotonic change in the properties of elements in a subset. This phenomenon discovered in 1915 Russian scientist EV Biron. This phenomenon is associated with the filling of the system at appropriate locations and d-f-shells, leading to hardening of an outer nucleus and s-p-electrons. This hardening is most strongly on the properties of the s-electron, at least of p-electrons, at least on the p-electrons, and even less on the d-electrons.

The nature of the change element properties over the period shown internal periodicity. Thus, during the transition from Be to B, despite an increase in the nuclear charge, atomic ionization energy decreases.

Consideration analogies elements led to the discovery of additional types of secondary periodicities and internal. Under the secondary periodicity mean a nonmonotonic change in the properties of elements and their compounds from the top down by subgroups, especially in the main. This was first noticed LI Biron and SA Shchukarev. The reason is due to the compression of atoms electrons filling the deep nucleus of an atom. This leads to lanthanide contraction - a decrease in the atomic radius from cerium to lutetium. The secondary frequency is well observed in the change of the elements of the ionization potentials.

in Mendeleev's system of elements, there is another type of periodicity in horizontal rows p. This so-called internal periodicity, the essence of which is non-monotonic change in the characteristics of these series of atoms, reflecting the stability of the valence electron orbitals. Most clearly the internal frequency can be illustrated by the change in the respective ionization potentials in horizontal rows.

25. Describe the hydrolytic ability of salts (give examples). Give a definition: The ionic product of water. Autoionization of water.

A basic salt is formed between a weak acid and a strong base. The basicity is due to the hydrolysis of the conjugate base of the (weak) acid used in the neutralization reaction. For example, sodium acetate formed between the weak acetic acid and the strong base NaOH is a basic salt. When the salt is dissolved, ionization takes place:

NaAc = Na⁺ + Ac^-In the presence of water, Ac^- undergo hydrolysis:

H₂O + Ac^- = HAc + OH^-And the equilibrium constant for this reaction is K_b of the conjugate base Ac^- of the acid HAc. Note the following equilibrium constants:

Thus, [HAc] [OH^-] [H⁺]

K_b = ----------- ---

[Ac^-] [H⁺]

[HAc] [OH^-][H⁺]

K_b = ---------- ---------

[Ac^-] [H⁺]

= K_w / K_a = 1.00e-14 / 1.75e-5 = 5.7e-10.

K_a K_b = K_wor

pK_a + pK_b = 14 for a conjugate acid-base pair. 

Titanium and zirconium hydroxophosphates in hydrogen and salt forms has been studied as ion exchangers. The compounds have been synthesized and converted into salt (Na or Ca) forms. Their hydrolytic stability as a function of the temperature of preliminary treatment has been tested. It has been shown that Zr - ionites are much more stable than Ti - ones; H - forms are more stable than salt ones; the thermal treatment at higher temperatures decreases the hydrolysis. The results are explained from the point of view of the ionite structure and hydrolysis mechanism. Ion - exchange properties of the materials have been tested by sorption of Pb ions. The thermal treatment has been shown to lower sorption capacity.

 One water molecule (acting as a base) can accept a hydrogen ion from a second one (acting as an acid). This will be happening anywhere there is even a trace of water - it doesn't have to be pure.

The self-ionization of water (also autoionization of water, and autodissociation of water) is an ionization reaction in pure water or an aqueous solution, in which a water molecule, H₂O,  loses the nucleus of one of its hydrogen atoms to become a hydroxide ion, OH⁻. The hydrogen nucleus, H⁺, immediately protonates another water molecule to form hydronium, H₃O+. It is an example of autoprotolysis, and exemplifies the amphoteric nature of water.