positive halogen atom
21alkali metal — Chem. any of the group of univalent metals including potassium, sodium, lithium, rubidium, cesium, and francium, whose hydroxides are alkalis. [1880 85] * * * Any of the six chemical elements in the leftmost group of the periodic table (lithium,… …
22organosulfur compound — ▪ chemical compound Introduction also spelled organosulphur compound , also called organic sulfur compound a subclass of organic substances that contain sulfur and that are known for their varied occurrence and unusual properties. They are… …
23reaction mechanism — Introduction in chemical reactions (chemical reaction), the detailed processes by which chemical substances are transformed into other substances. The reactions themselves may involve the interactions of atoms (atom), molecules (molecule),… …
24Technetium — molybdenum ← technetium → ruthenium Mn ↑ Tc ↓ Re …
25Ununoctium — ununseptium ← ununoctium → ununennium Rn ↑ Uuo ↓ (Uho) …
26Caesium — xenon ← caesium → barium Rb ↑ Cs ↓ Fr …
27iodine — /uy euh duyn , din/; in Chem. also /uy euh deen /, n. Chem. a nonmetallic halogen element occurring at ordinary temperatures as a grayish black crystalline solid that sublimes to a dense violet vapor when heated: used in medicine as an antiseptic …
28Ozone depletion — Image of the largest Antarctic ozone hole ever recorded (September 2006) Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth s… …
29oxidation–reduction reaction — ▪ chemical reaction Introduction also called redox reaction any chemical reaction in which the oxidation number of a participating chemical species changes. The term covers a large and diverse body of processes. Many oxidation– reduction… …
30Chemical bond — A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and… …
