has_part phenanthroline
An organic compound is virtually any ___MASK28___ that contains ___MASK89___ , although a consensus definition remains elusive and likely arbitrary . Organic compounds are rare terrestrially , but of central importance because all known life is based on organic compounds . The most basic petrochemicals are considered the building blocks of organic chemistry . ___MASK37___ ___MASK28___ ( or just compound if used in the context of chemistry ) is an entity consisting of two or more atoms , at least two from different elements , which associate via chemical bonds . There are four types of compounds , depending on how the constituent atoms are held together : molecules held together by covalent bonds , ionic compounds held together by ionic bonds , intermetallic compounds held together by metallic bonds , and certain complexes held together by coordinate covalent bonds . Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service ( CAS ): its CAS number . In coordination ___MASK25___ , a ligand is an ion or molecule ( functional group ) that binds to a central metal atom to form a coordination complex . The bonding with the metal generally involves formal donation of one or more of the ligand ' ___MASK67___ electron pairs . The nature of metal  ligand bonding can range from covalent to ionic . Furthermore , the metal  ligand bond order can range from one to three . Ligands are viewed as Lewis bases , although rare cases are known to involve Lewis acidic " ligand ." An ion is an ___MASK40___ or ___MASK37___ molecule in which the total number of electrons is not equal to the total number of protons , giving the ___MASK40___ or molecule ___MASK37___ net positive or negative electrical charge . Ions can be created , by either chemical or physical means , via ionization . Bond ___MASK42___ is the number of chemical bonds between ___MASK37___ pair of atoms . For example , in diatomic nitrogen N  N the bond ___MASK42___ is 3 , in acetylene the bond ___MASK42___ between the two ___MASK89___ atoms is also 3 , and the bond ___MASK42___ is 1 . Bond ___MASK42___ gives an indication of the stability of ___MASK37___ bond . An element with bond ___MASK42___ value 0 cannot exist , but compounds can have ___MASK37___ 0 bond value . ___MASK89___ ( from " coal ") is a chemical element with symbol ___MASK90___ and atomic number 6 . It is nonmetallic and tetravalent  making four electrons available to form covalent chemical bonds . Three isotopes occur naturally , ___MASK90___ and ___MASK90___ being stable , while ___MASK90___ is a radioactive isotope , decaying with a half - life of about 5 , 730 years . ___MASK89___ is one of the few elements known since antiquity . ___MASK37___ metal ( from Greek  " métallon ", " mine , quarry , metal ") is ___MASK37___ material ( an ___MASK72___ , compound , or alloy ) that is typically hard , opaque , shiny , and has ___MASK48___ electrical and thermal conductivity . Metals are generally malleable  that is , they can be hammered or pressed permanently out of shape without breaking or cracking  as well as fusible ( able to be fused or melted ) and ductile ( able to be drawn out into ___MASK37___ thin wire ). About 91 of the 118 elements in the periodic table are metals , the others are nonmetals or metalloids . Some elements appear in both metallic and non - metallic forms . ___MASK37___ molecule is an electrically neutral group of two or more atoms held together by chemical bonds . Molecules are distinguished from ions by their lack of electrical charge . However , in quantum physics , organic ___MASK25___ , and biochemistry , the term " molecule " is often used less strictly , also being applied to polyatomic ions . In ___MASK25___ , an ___MASK96___ pair or a Lewis pair consists of two electrons that occupy the same orbital but have opposite spins . The ___MASK96___ pair concept was introduced in a 1916 paper of Gilbert N . Lewis . Because electrons are fermions , the Pauli exclusion principle forbids these particles from having exactly the same quantum numbers . Therefore , the only way to occupy the same orbital , i . e . have the same orbital quantum numbers , is to differ in the spin quantum number . This limits the number of electrons in the same orbital to exactly two . In ___MASK25___ , a coordination complex consists of a central atom or ion , which is usually metallic and is called the " coordination centre ", and a surrounding array of bound molecules or ions , that are in turn known as " ligands " or complexing agents . Many metal - containing compounds , especially those of transition metals , are coordination complexes . A coordination complex whose centre is a metal atom is called a metal complex . In organic ___MASK25___ , functional groups are specific groups ( moieties ) of atoms or bonds within molecules that are responsible for the characteristic chemical reactions of those molecules . The same functional group will undergo the same or similar chemical reaction ( ___MASK67___ ) regardless of the size of the molecule it is a part of . However , its relative reactivity can be modified by other functional groups nearby . The atoms of functional groups are linked to each other and to the rest of the molecule by covalent bonds . Any subgroup of atoms of a compound also may be called a radical , and if a covalent bond is broken homolytically , the resulting fragment radicals are referred as free radicals . Functional groups can also be charged , e . g . in carboxylate salts (- COO ), which turns the molecule into a polyatomic ion or a complex ion . Phenanthroline ( phen ) is ___MASK37___ heterocyclic organic compound . It is ___MASK37___ white solid that is soluble in organic solvents . It is used as ___MASK37___ ligand in coordination ___MASK25___ , it forms strong complexes with most metal ions . In terms of its coordination properties , phen is similar to 2 , 2 ' - bipyridine ( bipy ) .