We'll return to this later on, as BH 3 has structural subtleties that will really take us into sexy territory. but when it does this, it acquires a negative charge, and it can only regain neutrality by losing one of its bonds - it really does have a split personality.īut the real interest, the 'skydiving', starts when we look at the trihydride of boron. It can achieve this chemistry because boron really does have two sides to it - it is set up to form 3 bonds with adjacent atoms, but even in this state, readily forms an extra bond in order to complete the 2 nd main shell of 8 electrons. Then there is the trifluoride - remember that acids were first classified as substances that could provide protons, but BF 3 is the archetypal Lewis acid, which doesn't have a proton in sight, yet is able to coordinate with lone pairs, allowing it to catalyse an array of reactions. Consider the nitride, for example - just the 2 elements at numbers 5 and 7 in the periodic table, but able to join forces to provide hard diamond or soft graphite-like structures, very similar to those of the 6 th element, carbon. But its unexpected side starts to emerge when you look at some simple compounds of boron. I don't know anyone who thinks the element boron has anything interesting about it. Boron is usually isolated as a brown, amorphous solid. Political stability of top reserve holderĪ percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators. The higher the value, the larger risk there is to supply.Ī percentile rank for the political stability of the top producing country, derived from World Bank governance indicators. The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply. The percentage of an element produced in the top producing country. Low = substitution is possible with little or no economic and/or performance impact
Medium = substitution is possible but there may be an economic and/or performance impact High = substitution not possible or very difficult. The availability of suitable substitutes for a given commodity. A higher recycling rate may reduce risk to supply. The percentage of a commodity which is recycled. The number of atoms of the element per 1 million atoms of the Earth’s crust. This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores. The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems.ĭata for this section been provided by the British Geological Survey.Īn integrated supply risk index from 1 (very low risk) to 10 (very high risk). Where more than one isotope exists, the value given is the abundance weighted average.Ītoms of the same element with different numbers of neutrons. This is approximately the sum of the number of protons and neutrons in the nucleus. The mass of an atom relative to that of carbon-12. The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.ĭensity is the mass of a substance that would fill 1 cm 3 at room temperature. The temperature at which the liquid–gas phase change occurs. The temperature at which the solid–liquid phase change occurs.
The arrangements of electrons above the last (closed shell) noble gas. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f). The atomic number of each element increases by one, reading from left to right.Įlements are organised into blocks by the orbital type in which the outer electrons are found.
Members of a group typically have similar properties and electron configurations in their outer shell.Ī horizontal row in the periodic table.
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