Group 14 periodicity

This article addresses the periodicity displayed by the Group 14 elements but excluding, largely, ununquadium (element 114) about which virtually nothing is known. One could predict the properties of ununquadium based upno those of the higher elements and this is left as an exercise for the reader.

Nature of the elements

The elements become increasingly metallic down the group. Carbon, at the top, is a typical non-metal while silicon is a semiconductor profoundly important to the electronics industries. Tin and lead are very metallic although one modification of tin known as grey tin has the same diamond structure as does germanium and silicon. The elements lower down the group form complexes while carbon does not. The melting points of the elements decrease down the group as the elements become increasingly metallic.

Multiple bonds

Carbon often forms multiple bonds, both with itself (as in ethene and ethyne) and with other elements such as oxygen (as in carbon dioxide and ketones). In contrast, silicon, germanium, and tin only form analogues of ethene (albeit non-planar) when the elements possess bulky substituents. While the C=C π-bond formed through the overlap of C 2p-orbitals is strong, those lower down the group are much less strong. This also explains why graphite is stable while there are no analogues of graphite lower down the group. Carbon dioxide, CO₂, possesses two carbon-oxygen double bonds (O=C=O) while the corresponding silicon dioxide, SiO₂, possesses an extended lattice structure. This is because the π-bond formed through the overlap of p-orbitals on carbon and oxygen is strong as the overlap is favourable, while lower down the group the π-overlap is less efficient.

Hydrides

The hydrides MX₄ are known for all the elements except ununquadium although the lead compound (plumbane, PbH₄) is poorly characterized. Each is a covalent molecule. The parent hydride for carbon is methane, CH₄, and there is an extensive range of compounds called alkanes of the type C_nH_2n+2 (methane, ethane, propane, butane....). There are relatively few of the corresponding silicon hydrides (silanes) and they are spontaneously flammable. The germane GeH₄ is known while the stannane SnH₄, a colourless gas, decomposes to tin at about 0°C.

Halides

Two types of halide for this group are known: MX₂ and MX₄. The M(IV) halides dominate the top of the group while the M(II) halides dominate at the bottom. All the M(IV) halides MX₄ (M = C, Si, Ge; X = F, Cl, Br, I) are all known for the three elements carbon, silicon, and germanium at the top of the group. However, as the group is descended, the stability of the M(II) state increases relative to the M(IV) state. None of the dihalides MX₂ exist independently for carbon or silicon while most of the divalent halides MX₂ are known for germanium in addition to the germanium tetrahalides. At the bottom of the group the most stable lead halides are PbX₂ and the only known tetrahalide seems to be PbCl₄ (this decomposes exothermically to PbCl₂ and chlorine gas).

Oxides

Ionization Energy

Here is a list of the elements sorted by alphabetically by element name.

List of elements sorted by symbol

Submitted by WebElements on 12 April 2006 - 2:38pm.

• General and introductory chemistry

Here is a list of the elements sorted by element symbol.

List of elements by atomic number

Submitted by WebElements on 12 April 2006 - 2:33pm.

• General and introductory chemistry

Here is a list of the elements sorted by atomic number.

The Group 1 elements

Submitted by WebElements on 12 April 2006 - 1:41pm.

• Caesium
• Francium
• Hydrogen
• Lithium
• Potassium
• Rubidium
• Sodium
• Ununennium
• General and introductory chemistry
• Group 1

The Group 1 elements other than hydrogen are called the alkali metals. The Group 1 elements are:

• Hydrogen
• Lithium
• Sodium
• Potassium
• Rubidium
• Caesium
• Francium

The Group 1 metals are all highly reactive silvery metals that are so reactive to air and moisture that they must be stored under an inert atmosphere or oil. They are all soft and can be cut easily with a knife.

Hydrogen is usually placed at the top of the Group but is not a Group 1 metal.

The electronic configuration of the elements all consist of a lone s-electron outside an inner core of electron corresponding to the previous inert gas.

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The Group 2 elements

Submitted by WebElements on 12 April 2006 - 1:41pm.

• Barium
• Beryllium
• Calcium
• Magnesium
• Radium
• Strontium
• General and introductory chemistry
• Group 2

The Group 2 elements are called the alkaline earth metals. The Group 2 elements are:

• Beryllium
• Magnesium
• Calcium
• Strontium
• Barium
• Radium

The electronic configuration of the elements all consist of two s-electrons outside an inner core of electron corresponding to the previous inert gas: the group configuration is therefore ns².

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Janet periodic table

Submitted by WebElements on 12 April 2006 - 1:20pm.

• General and introductory chemistry

The Janet periodic table

The Janet periodic table is an excellent alternative periodic table and organises elements according to orbital filling. Therefore, hydrogen is above lithium on the grounds they are both ns¹, and helium above beryllium on the grounds they are both ns². Current Group numbers are displayed to help orientation with the standard table.

This is the extended version of the periodic table

The Mendeleev Periodic Table

This table shows the form of Mendeleev's Periodic Table of the chemical elements as published in 1872. The heading "Reihen" means "Row" and the heading "Gruppe" means "Group". The symbols R²O and RH⁴, etc., are written in the style of the time which uses superscripts to denote the number of atoms in molecules rather than the current style which uses subscripts. The gaps marked with hyphens ("-") represent chemical elements deduced by Mendeleev as existing but unknown in 1872. He was able to predict with considerable success the properties of some of the missing chemical elements such as germanium.

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