Main-group element Main-group element In chemistry and atomic physics, the main group is the group of elements whose lightest members are represented by helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine as arranged in the periodic table of the elements. The main group includes the elements (except hydrogen, which is sometimes not included) in groups 1 and 2 (s-block), and groups 13 to 18 (p-block). The s-block elements are primarily characterised by one main oxidation state, and the p-block elements, when they have multiple oxidation states, often have common oxidation states separated by two units. Main-group elements (with some of the
Canonical link element document. 11. Site Host https://sitehostnp.com/canonicalization/canonical-link-element/. What s "rel=canonical" link element and how it should be used for search engines. Published on 14 June 2018. Canonical link element A canonical link element is an HTML element that helps webmasters prevent duplicate content issues in search engine optimization by specifying the "canonical" or "preferred" version of a web page. It is described in RFC 6596, which went live in April 2012. A major problem for search engines is to determine the original source for documents that are available on multiple URLs. Content duplication can happen in a many ways, including: Duplicate content