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A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Edexcel (also known since 2013 as Pearson Edexcel) [2] is a British multinational education and examination body formed in 1996 and wholly owned by Pearson plc since 2005. It is the only privately owned examination board in the United Kingdom. [3] Its name is a portmanteau term combining the words education and excellence.
However, in the Physics paper 1 exam, a topic that was stated as "Not Assessed" came up; AQA accepted the mistake and awarded all students the full 9 marks to the question. [70] Also, in 2022, a question on one of the higher Maths papers was leaked hours before students sat them. The exam board Edexcel apologised and conducted a full ...
The halogens (/ ˈ h æ l ə dʒ ə n, ˈ h eɪ-,-l oʊ-,-ˌ dʒ ɛ n / [1] [2] [3]) are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors [4] would exclude tennessine as its chemistry is unknown and is theoretically expected to ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 13 January 2025. Educational assessment For other uses, see Exam (disambiguation) and Examination (disambiguation). Cambodian students taking an exam in order to apply for the Don Bosco Technical School of Sihanoukville in 2008 American students in a computer fundamentals class taking an online test in ...
The Hill system (or Hill notation) is a system of writing empirical chemical formulae, molecular chemical formulae and components of a condensed formula such that the number of carbon atoms in a molecule is indicated first, the number of hydrogen atoms next, and then the number of all other chemical elements subsequently, in alphabetical order ...
Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...
Printable version; In other projects Wikidata item; Appearance. move to sidebar hide. EC number may refer to: Enzyme Commission number for ...