In chemistry, a group (also known as a family) is a column of elements in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table, but the f-block columns (between groups 2 and 3) are not numbered. The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms (i.e., the same core charge), as most chemical properties are dominated by the orbital location of the outermost electron.
There are three systems of group numbering. The modern numbering group 1 to group 18 is recommended by the International Union of Pure and Applied Chemistry (IUPAC). It replaces two older naming schemes that were mutually confusing. Also, groups may be identified by their topmost element or have a specific name. For example, group 16 is variously described as oxygen group and chalcogen.
CAS and old IUPAC numbering
Two earlier group number systems exist: CAS (Chemical Abstracts Service) and old IUPAC. Both use numerals (Arabic or Roman) and letters A and B. Both systems agree on the numbers. The numbers indicate approximately the highest oxidation number of the elements in that group, and so indicate similar chemistry with other elements with the same numeral. The number proceeds in a linearly increasing fashion for the most part, once on the left of the table, and once on the right (see List of oxidation states of the elements), with some irregularities in the transition metals. However, the two systems use the letters differently. For example, potassium (K) has one valence electron. Therefore, it is located in group 1. Calcium (Ca) is in group 2, for it contains two valence electrons.
In shooting, a shot grouping, or simply grouping, is the placement of multiple shots on a target, the shots taken in one shooting session. The closeness of the grouping, the nearness of all the shots to each other, is a measure of the accuracy of a weapon, and a measure of the shooter's consistency and skill.
Uses of the term
For firearms that shoot one round at a time, a shot grouping can be used to measure the accuracy of the system comprised out of weapon as well as the precision and uniformity of the ammunition by fixing the weapon into position on a test mount, and aiming it at a target. Multiple shots using rounds from same type and batch are fired to observe how the weapon groups the shots. If a person holds the weapon and shoots it, the grouping measures the combination of the person's skill and the weapon's accuracy.
In shotgun shooting, the grouping is also called the pattern. The pattern is the spread of shot from a single shotgun shell, measured as the smallest circle containing all the shots on the target. The barrel of a shotgun is designed to deliver a wide or narrow grouping, depending on the expected use. Shooting at close range indicates a cylinder bore barrel to deliver a wide grouping, while for hunting at longer distances such as 50 yards or meters, a choke is recommended for a tighter grouping.
Environmental groups contend that TVA and its local power utilities are doing less than most other utilities to promote energy efficiency, noting that TVA limited some of the loan programs and incentives it once offered to homeowners to buy more energy-efficient heat pumps and other appliances.
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Facebook has signed a deal to buy renewable energy in India from a local firm’s ... In Singapore, Facebook has announced similar partnerships with energy providers Sunseap Group, Terrenus Energy and Sembcorp Industries on projects that can produce 160MW of solar power, Parekh said.
In Singapore, Facebook has announced similar partnerships with energy providers Sunseap Group, Terrenus Energy and Sembcorp Industries on projects that can produce 160 MW of solar power, Parekh said ...Data centres driving tech companies like Facebook use up as much as 1% of the world's total energy, the International Energy Agency said last year.
In March, gasoline prices rose 9.1% and natural gas rose 2.5%, contributing to an overall increase of 5% for energy costs last month ... “When energy prices rise, the poor and middle class suffer the most,” said Daniel Turner, founder of Power the Future, an advocacy group for energy workers.
“We are pleased to have executed an ESA with MHIGroup, a widely recognised leader in commercial-scale carbon capture technology,” said Matt Schatzman, NextDecade’s chairman and CEO... MHI Group is committed to being an innovative solution provider as the energy industry transitions to lower carbon options.
In other action Tuesday,. the board in 5-0 votes.. — Approved moving forward with the concept of a second EnergySystemsGroup agreement to put in more energy efficiency improvements in the schools, with the tentative language guaranteeing $350,000 a year in energy savings over a 15-year period using mostly low-interest loans of up to $5 million ... ....