Periodic Table is probably WRONG

The many different forms of periodic table have prompted the question of whether there is an optimal or definitive form of periodic table. The answer to this question is thought to depend on whether the chemical periodicity seen to occur among the elements has an underlying truth, effectively hard-wired into the universe, or if any such periodicity is instead the product of subjective human interpretation, contingent upon the circumstances, beliefs and predilections of human observers. An objective basis for chemical periodicity would settle the questions about the location of hydrogen and helium, and the composition of group 3. Such an underlying truth, if it exists, is thought to have not yet been discovered. In its absence, the many different forms of periodic table can be regarded as variations on the theme of chemical periodicity, each of which explores and emphasizes different aspects, properties, perspectives and relationships of and among the elements.^{[n 19]} The ubiquity of the standard or medium-long periodic table is thought to be a result of this layout having a good balance of features in terms of ease of construction and size, and its depiction of atomic order and periodic trends.

Holmium (new) - Periodic Table of Videos

Holmium is a chemical element with symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a rare earth element. Holmium was discovered by Swedish chemist Per Theodor Cleve. Its oxide was first isolated from rare earth ores in 1878 and the element was named after the city of Stockholm.

Elemental holmium is a relatively soft and malleable silvery-white metal. It is too reactive to be found uncombined in nature, but when isolated, is relatively stable in dry air at room temperature. However, it reacts with water and rusts readily, and will also burn in air when heated.

Holmium is found in the minerals monazite and gadolinite, and is usually commercially extracted from monazite using ion exchange techniques. Its compounds in nature, and in nearly all of its laboratory chemistry, are trivalently oxidized, containing Ho(III) ions. Trivalent holmium ions have fluorescent properties similar to many other rare earth ions (while yielding their own set of unique emission light lines), and holmium ions are thus used in the same way as some other rare earths in certain laser and glass colorant applications.

Holmium has the highest magnetic permeability of any element and therefore is used for the polepieces of the strongest static magnets. Because holmium strongly absorbs neutrons, it is also used as a burnable poison in nuclear reactors.

Underwater Sodium - Periodic Table of Videos

Aqueous solutions[edit]

Sodium tends to form water-soluble compounds, such as halides, sulfates, nitrates, carboxylates and carbonates. The main aqueous species are the aquo complexes [Na(H₂O)_n]⁺, where n = 4–6.^[24] The high affinity of sodium for oxygen-based ligands is the basis of crown ethers; macrolide antibiotics, which interfere with Na⁺ transport in the infecting organism, are functionally related and more complex.^{[citation needed]}

Direct precipitation of sodium salts from aqueous solutions is rare because sodium salts typically have a high affinity for water; an exception is sodium bismuthate (NaBiO₃).^[25] Because of this, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic solvent, such as ethanol; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol.^[26] Crown ethers, like 15-crown-5, may be used as a phase-transfer catalyst.^[27]

Sodium content in bulk may be determined by treating with a large excess of uranyl zinc acetate; the hexahydrate (UO₂)₂ZnNa(CH₃CO₂)·6H₂O precipitates and can be weighed. Caesium and rubidium do not interfere with this reaction, but potassium and lithium do.^[28] Lower concentrations of sodium may be determined by atomic absorption spectrophotometry^[29] or by potentiometry using ion-selective electrodes.^[30]