Basic Flowchart Symbols and Meaning

The vector stencils library "Chemical elements" contains 118 icon symbols of chemical elements for drawing atoms, structural formulas and ball-and-stick models of inorganic and organic molecules and ions, and schemes of chemical reaction mechanisms.
"In chemistry, the ball-and-stick model is a molecular model of a chemical substance which is to display both the three-dimensional position of the atoms and the bonds between them. The atoms are typically represented by spheres, connected by rods which represent the bonds. Double and triple bonds are usually represented by two or three curved rods, respectively. In a good model, the angles between the rods should be the same as the angles between the bonds, and the distances between the centers of the spheres should be proportional to the distances between the corresponding atomic nuclei. The chemical element of each atom is often indicated by the sphere's color." [Ball-and-stick model. Wikipedia]
The chemical symbols example "Design elements - Chemical elements" was created using the ConceptDraw PRO software extended with the Chemistry solution from the Science and Education area of ConceptDraw Solution Park.

The vector stencils library "Aromatics" contains 23 symbols of aromatic rings for chemical drawing of molecular structural formulas and reaction mechanism schemes in organic chemistry.
"In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Aromaticity can also be considered a manifestation of cyclic delocalization and of resonance. This is usually considered to be because electrons are free to cycle around circular arrangements of atoms that are alternately single- and double-bonded to one another. These bonds may be seen as a hybrid of a single bond and a double bond, each bond in the ring identical to every other. This commonly seen model of aromatic rings, namely the idea that benzene was formed from a six-membered carbon ring with alternating single and double bonds (cyclohexatriene), was developed by Kekulé (see History section below). The model for benzene consists of two resonance forms, which corresponds to the double and single bonds superimposing to give rise to six one-and-a-half bonds. Benzene is a more stable molecule than would be expected without accounting for charge delocalization. ... Types of aromatic compounds. The overwhelming majority of aromatic compounds are compounds of carbon, but they need not be hydrocarbons. 1. Neutral homocyclics. Benzene, as well as most other annulenes (cyclodecapentaene excepted) with the formula CnHn where n is an even number, such as cyclotetradecaheptaene. 2. Heterocyclics. In heterocyclic aromatics (heteroaromats), one or more of the atoms in the aromatic ring is of an element other than carbon. This can lessen the ring's aromaticity, and thus (as in the case of furan) increase its reactivity. Other examples include pyridine, pyrazine, imidazole, pyrazole, oxazole, thiophene, and their benzannulated analogs (benzimidazole, for example). 3. Polycyclics. Polycyclic aromatic hydrocarbons are molecules containing two or more simple aromatic rings fused together by sharing two neighboring carbon atoms (see also simple aromatic rings). Examples are naphthalene, anthracene, and phenanthrene. 4. Substituted aromatics. Many chemical compounds are aromatic rings with other functional groups attached. Examples include trinitrotoluene (TNT), acetylsalicylic acid (aspirin), paracetamol, and the nucleotides of DNA. 5. Atypical aromatic compounds. Aromaticity is found in ions as well: the cyclopropenyl cation (2e system), the cyclopentadienyl anion (6e system), the tropylium ion (6e), and the cyclooctatetraene dianion (10e). Aromatic properties have been attributed to non-benzenoid compounds such as tropone. Aromatic properties are tested to the limit in a class of compounds called cyclophanes. A special case of aromaticity is found in homoaromaticity where conjugation is interrupted by a single sp³ hybridized carbon atom. When carbon in benzene is replaced by other elements in borabenzene, silabenzene, germanabenzene, stannabenzene, phosphorine or pyrylium salts the aromaticity is still retained. Aromaticity also occurs in compounds that are not carbon-based at all. Inorganic 6-membered-ring compounds analogous to benzene have been synthesized. Hexasilabenzene (Si6H6) and borazine (B3N3H6) are structurally analogous to benzene, with the carbon atoms replaced by another element or elements. In borazine, the boron and nitrogen atoms alternate around the ring." [Aromaticity. Wikipedia]
The organic compound structural formulas example "Aromatics - Vector stencils library" was created using the ConceptDraw PRO software extended with the Chemistry solution from the Science and Education area of ConceptDraw Solution Park.