Conventions in Chemistry - The ACS Style Guide (ACS Publications)

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CHAPTER 13

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Conventions in Chemistry

T

his chapter presents a quick reference guide for the use of typefaces (roman, italic, and bold), Greek letters, superscripts and subscripts, and special symbols that are commonly used in chemistry. Appendix 13-1 presents the symbols for commonly used physical quantities. Detailed recommendations from the International Union of Pure and Applied Chemistry (IUPAC, http://www.iupac.org) are given in the book titled Quantities, Units and Symbols in Physical Chemistry, 2nd edition, nicknamed the “green book”, published by Blackwell Science, Oxford, U.K., 1993. Updates are published as articles in the journal Pure and Applied Chemistry. Detailed recommendations from the International Organization for Standardization (ISO, http://www.iso.org) are given in the ISO Standards Handbook 2, Quantities and Units, published by ISO, Geneva, Switzerland, 1993. Some individual standards have been amended, and their updates are available at http:// www.iso.org/iso/en/prods-service/ISOstore/store.html. The National Institute of Standards (NIST) Special Publication 330, 2001 Edition, available at http:// physics.nist.gov/Pubs/SP330/sp330.pdf, is the U.S. updated edition of the English version of the Bureau International des Poids et Mesures. The booklet The International System of Units (SI), 7th ed., published by the International Bureau of Weights and Measures (BIPM), Sèvres, France, 1998, is the definitive reference on SI units. Some books and journals follow IUPAC recommendations for representations of various chemical conventions. Some specify the use of ISO standards. Others are less stringent as long as the manuscript is consistent in usage within itself. Always consult the author guidelines.

Copyright 2006 American Chemical Society In The ACS Style Guide; Coghill, A., et al.; The ACS Style Guide; American Chemical Society: Washington, DC, 2006.

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➤ The ACS Style Guide

Subatomic Particles and Quanta ➤ Use lowercase Latin or Greek letters for abbreviations for subatomic particles. alpha particle beta particle deuteron electron helion muon

α β d e h

µ±

neutrino neutron photon pion proton triton

νe n

γ π

p t


➤ Indicate electric charges with the appropriate superscript (+, –, or 0). n0 e+ e–

π±

If the symbols p and e are used without indication of charge, they refer to positive proton and negative electron, respectively.

Electronic Configuration ➤ Denote electron shells with the uppercase roman letters K, L, M, and N. ➤ Name electron subshells and atomic orbitals with the lowercase roman letters

s, p, d, and f. Write principal energy levels 1–7 on the line and to the left of the letter; give the number of electrons in the orbital as a superscript to the right of the letter. Specify orbital axes with italic subscripts. 7s electron 3d44s4p2 configuration 2 5f ions pxpypz 5f orbital dxzdyzdxy 6d orbital dz2 sp3 hybrid orbital dx2–y2 fn–3ds2 configuration The ground state of boron is 1s22s22px12py02pz0. The valence-shell configuration of nitrogen is 2s22px12py12pz1. The electronic configuration of potassium is 1s22s22p63s23p64s1. The valence-electron configuration is described by 5d106s1.

➤ Use Greek letters for some bonding orbitals and the bonds they generate. π bond σ orbital σ∗ orbital

In The ACS Style Guide; Coghill, A., et al.; The ACS Style Guide; American Chemical Society: Washington, DC, 2006.

Chapter 13: Conventions in Chemistry

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257

➤ Name the electronic states of atoms with the uppercase roman letters S, P, D, F,

G, H, I, and K, corresponding to quantum numbers l = 0–7. Use the corresponding lowercase letters to indicate the orbital angular momentum of a single electron. The left superscript is the spin multiplicity; the right subscript is the total angular momentum quantum number J. 2S 0 2s 0 8F 1/2 8f 1/2

4P 1/2 4p 1/2 8G 1/2 8g 1/2

7F 0 7f 0 2P 3/2

2p 3/2 7D 1 7d 1


➤ Name the electronic states of molecules with the uppercase roman letters A, B,

E, and T; the ground state is X. Use the corresponding lowercase letters for oneelectron orbitals. A tilde (~) is added for polyatomic molecules. The subscripts describe the symmetry of the orbital. Ã 2 A1g A2g ã

2

a1g a2g 3 B1 3 b1

Eg E2g eg

e2g T2g t2g

Chemical Elements and Formulas ➤ Write the names of the chemical elements in roman type and treat them as

common nouns. oxygen seaborgium uranium

francium helium hydrogen

calcium californium carbon einsteinium

➤ Write the symbols for the chemical elements in roman type with an initial

capital letter. Ca Cf C

Es Fr He

H O

Sg U

The complete list of chemical elements and symbols is given in Table 13-1. ➤ Even when symbols are used, the element’s name is pronounced. Therefore,

choose the article (a or an) preceding the element symbol to accommodate the pronunciation of the element name. (This usage does not apply to isotopes, as described in the section on isotopes.) a Au electrode (pronounced “a gold electrode”) a N-containing compound (pronounced “a nitrogen-containing compound”) a He–Ne laser (pronounced “a helium–neon laser”)


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Table 13-1. Atomic Weights of the Elements 2001 Name Actinium Aluminum Americium Antimony Argon Arsenic Astatine Barium Berkelium Beryllium Bismuth Bohrium Boron Bromine Cadmium Calcium Californium Carbon Cerium Cesium Chlorine Chromium Cobalt Copper Curium Dubnium Dysprosium Einsteinium Erbium Europium Fermium Fluorine Francium Gadolinium Gallium Germanium Gold Hafnium Hassium Helium Holmium Hydrogen Indium Iodine Iridium Iron Krypton Lanthanum

Sym. Ac Al Am Sb Ar As At Ba Bk Be Bi Bh B Br Cd Ca Cf C Ce Cs Cl Cr Co Cu Cm Db Dy Es Er Eu Fm F Fr Gd Ga Ge Au Hf Hs He Ho H In I Ir Fe Kr La

No. 89 13 95 51 18 33 85 56 97 4 83 107 5 35 48 20 98 6 58 55 17 24 27 29 96 105 66 99 68 63 100 9 87 64 31 32 79 72 108 2 67 1 49 53 77 26 36 57

Atomic Wt. Notes * 26.981538(2) * g 121.760(1) g, r 39.948(1) 74.92160(2) * 137.327(7) * 9.012182(3) 208.98038(2) * g, m, r 10.811(7) 79.904(1) g 112.411(8) g 40.078(4) * g, r 12.0107(8) g 140.116(1) 132.90545(2) g, m, r 35.453(2) 51.9961(6) 58.933200(9) r 63.546(3) * * g 162.500(1) * g 167.259(3) g 151.964(1) * 18.9984032(5) * g 157.25(3) 69.723(1) 72.64(1) 196.96655(2) 178.49(2) * 4.002602(2) g, m 164.93032(2) g, m, r 1.00794(7) 114.818(3) 126.90447(3) 192.217(3) 55.845(2) g, m 83.798(2) 138.9055(2) g

Name Lawrencium Lead Lithium Lutetium Magnesium Manganese Meitnerium Mendelevium Mercury Molybdenum Neodymium Neon Neptunium Nickel Niobium Nitrogen Nobelium Osmium Oxygen Palladium Phosphorus Platinum Plutonium Polonium Potassium Praseodymium Promethium Protactinium Radium Radon Rhenium Rhodium Rubidium Ruthenium Rutherfordium Samarium Scandium Seaborgium Selenium Silicon Silver Sodium Strontium Sulfur Tantalum Technetium Tellurium

Sym. Lr Pb Li Lu Mg Mn Mt Md Hg Mo Nd Ne Np Ni Nb N No Os O Pd P Pt Pu Po K Pr Pm Pa Ra Rn Re Rh Rb Ru Rf Sm Sc Sg Se Si Ag Na Sr S Ta Tc Te

No. Atomic Wt. Notes 103 * g, r 82 207.2(1) g, m, r 3 6.941(2)† g 71 174.967(1) 12 24.3050(6) 25 54.938049(9) 109 * 101 * 80 200.59(2) g 42 95.94(2) g 60 144.24(3) g, m 10 20.1797(6) 93 * 28 58.6934(2) 41 92.90638(2) g, r 7 14.0067(2) 102 * g 76 190.23(3) g, r 8 15.9994(3) g 46 106.42(1) 15 30.973761(2) 78 195.078(2) 94 * 84 * 19 39.0983(1) 59 140.90765(2) 61 * 91 231.03588(2)* 88 * 86 * 75 186.207(1) 45 102.90550(2) g 37 85.4678(3) g 44 101.07(2) 104 * g 62 150.36(3) 21 44.955910(8) 106 * r 34 78.96(3) r 14 28.0855(3) 47 107.8682(2) g 11 22.989770(2) g, r 38 87.62(1) g, r 16 32.065(5) 73 180.9479(1) 43 * g 52 127.60(3) Continued on next page



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Table 13-1. Atomic Weights of the Elements 2001—Continued


Name Terbium Thallium Thorium Thulium Tin Titanium Tungsten Ununbium Ununhexium Ununnilium

Sym. Tb Tl Th Tm Sn Ti W Uub Uuh Uun

No. 65 81 90 69 50 22 74 112 116 110

Atomic Wt. Notes 158.92534(2) 204.3833(2) 232.0381(1)* g 168.93421(2) g 118.710(7) 47.867(1) 183.84(1) * * *

Name Ununquadium Unununium Uranium Vanadium Xenon Ytterbium Yttrium Zinc Zirconium

Sym. No. Atomic Wt. Notes Uuq 114 * Uuu 111 * U 92 238.02891(3)* g, m V 23 50.9415(1) g, m Xe 54 131.293(6) g Yb 70 173.04(3) Y 39 88.90585(2) Zn 30 65.409(4) g Zr 40 91.224(2)

Notes: Scaled to the relative atomic mass, Ar(12C) = 12, where 12C is a neutral atom in its nuclear and electronic ground state. The atomic weights of many elements are not invariant but depend on the origin and treatment of the material. The standard values of Ar(E) and the uncertainties (in parentheses following the last significant figure to which they are attributed) apply to elements of natural terrestrial origin. The footnotes to this table elaborate the types of variation that may occur for individual elements and that may be larger than the listed uncertainties of values of Ar(E). Names of elements with atomic numbers 110 to 116 are provisional. *Element has no stable nuclides. However, three such elements (Pa, Th, and U) do have a characteristic terrestrial isotopic composition, and for these an atomic weight is tabulated. †Commercially available Li materials have atomic weights that range between 6.939 and 6.996; if a more accurate value is required, it must be determined for the specific material. g Geological specimens are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such specimens and that given in the table may exceed the stated uncertainty. m Modified isotopic compositions may be found in commercially available material because it has been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur. r Range in isotopic composition of normal terrestrial material prevents a more precise Ar(E) being given; the tabulated Ar(E) value should be applicable to any normal material. Source: Reprinted with permission from IUPAC, 2003. Copyright 2003 IUPAC.

➤ Write the names of chemical compounds in roman type and treat them

as common nouns. (Names for chemical compounds are discussed further in Chapter 12.) isopropyl iodide magnesium sulfate mercuric sulfate methyl salicylate phenol sodium hydroxide

benzaldehyde calcium carbonate chlorobenzene ethanol hydrochloric acid iron(III) nitrate

➤ Use roman type for the symbols for chemical compounds. BaSO4 C2H5OH C6H5Cl C6H5OH CaCO3

CH3COOH Fe(NO3)3 H3PO4 HCl HgSO4

NaOH Ni3P2O8 P2S5 VF5 Zn(C2H3O2)2


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➤ You may use both chemical symbols and element names in text, but it is best to

use one or the other consistently. Do not mix symbols and words within a name. NaCl or sodium chloride, not Na chloride

➤ Unnamed elements may be designated by using the atomic number (for


example, element 125). They may also be designated by using the systematic name or symbol devised by IUPAC for elements of atomic number greater than 100 that have not yet received trivial names. In this system, an element name consists of a series of numerical roots corresponding to the numerals in the atomic number of the element, followed by “ium”. The roots are as follows: 0 1 2 3

4 5 6

nil un bi tri

7 8 9

quad pent hex

sept oct enn

The symbols consist of the first letters of the numerical roots.

examples element 146 element 187 element 209 element 290 element 501 element 502 element 503 element 900

unquadhexium unoctseptium binilennium biennilium pentnilunium pentnilbium pentniltrium ennilnilium

Uqh Uos Bne Ben Pnu Pnb Pnt Enn

Drop the final “n” in “enn” when it is followed by “nil” (see elements 290 and 900) and the final “i” in “bi” and “tri” when they are followed by “ium” (see elements 502 and 503). ➤ You may use common abbreviations for organic groups in formulas and

structures, but not in text. These (and only these) abbreviations need not be defined. Ac Ar Bu i-Bu sec-Bu t-Bu Bz

acetyl aryl butyl isobutyl sec-butyl tert-butyl benzoyl

Bn, Bzl Et Me Ph Pr i-Pr R, R′

benzyl ethyl methyl phenyl propyl isopropyl alkyl

➤ Use square brackets in formulas for coordination entities. [Cr(C6H6)2] K[PtCl3(C2H4)]



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261

➤ In the formula for an addition compound, use a centered dot, closed up on

each side. (Although the IUPAC books show a space on each side, this spacing would wreak havoc with many typesetting systems.) BH3·NH3 Ni(NO3)2·2Ni(OH)2

Water of hydration follows a centered dot, closed up on each side. Na2SO4·10H2O Zn(NO3)2·H2O


➤ Use either a slash or an en dash between components of a mixture, but not a

colon. dissolved in 5:1 glycerin/water dissolved in 5:1 glycerin–water the metal/ligand (1:1) reaction mixture the metal–ligand (1:1) reaction mixture the metal–ligand (1/1) reaction mixture the methane/oxygen/argon (1/50/450) matrix the methane/oxygen/argon (1:50:450) matrix

Reference to the Periodic Table ➤ Always use lowercase for the word “group”, even with a specific number. group 15 elements group IVB elements

➤ Always use lowercase for the words “periodic table”. The elements in group 8 of the periodic table include Fe, Ru, and Os.

Atoms and Molecules Nuclide descriptors are specified with superscripts and subscripts to the element symbol, as follows.

Use the Left Superscript for Mass Number ➤ The mass number of an atom is usually shown only for isotopes or in dis-

cussions of isotopes. 12C 35Cl 32S


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Use the Left Subscript for Atomic Number ➤ The atomic number of an atom is usually used only in discussions of nuclear

chemistry. 6C 16S

Use the Right Superscript for Ionic Charge ➤ The charge number is followed by the sign of the ionic charge. When the


charge number is 1, only the sign is used. Ca2+ Na+ NO3–

➤ Stagger the subscript and superscript; do not align them. The subscript comes

first with ionic charge. PO43–

➤ Do not use multiple plus or minus signs, and do not circle the charge. Hg2+ (not Hg++)

Use the Right Asterisk for Excited Electronic State He∗ NO∗

Use the Right Superscript for Oxidation Number ➤ You may use superscript roman numerals for oxidation numbers. In for-

mulas, do not use numbers on the line to avoid confusion with the symbols for iodine or vanadium. CoIII FeIICl2 MnIII/IV MnIII–MnIV

MnIII/MnIV MnIVO2 (NH3)2PtII Ni0

O–II PbIVO2 RuII–RuIII RuII/RuIII

➤ Stagger the subscript and superscript; do not align them. The subscript follows the superscript with oxidation number. PbII2

➤ You may also write oxidation numbers on the line in parentheses closed up

to the element name or symbol.



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cobalt(III) or Co(III) copper(II) or Cu(II) diammineplatinum(II) ferrate(VI) ion iron(II) or Fe(II) iron(II) chloride manganese(IV) oxide Mn(III)–Mn(IV) complex Mn(III)/Mn(IV) complex potassium tetracyanonickelate(0)


Use the Right Subscript for Number of Atoms ➤ With an element symbol, use a subscript to indicate the number of atoms,

whether in formulas or in narrative text. Al2O3 (CH3)4C H2S Fe3 C6 NH4 C6H5CH3 FeSi2 The C60 fullerene molecule is shaped like a soccer ball.

➤ With an element name, follow the usual conventions for numbers in text. Molecules composed of 60 carbon atoms are shaped like soccer balls. In this reaction, three hydrogen atoms are lost.

Atom in a Specific Position ➤ Use either words or symbols and numbers on the line to refer to an atom in a

specific position. at the carbon in the 6-position or at C6 or at C-6 the atom in the β-position or the β atom

Isotopes ➤ Specify the isotope of an element by a mass number written as a left superscript to the element symbol. 13

C N 32 S 29 Si 235 U 15


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➤ Alternatively, indicate an isotope by using the spelled-out element name

hyphenated to its mass number. carbon-14 uranium-235

➤ In either case, the isotope name or symbol is pronounced first, then the num-


ber. Thus, 14C is pronounced “c fourteen”. Consequently, choose the article (a or an) preceding the isotope to accommodate the pronunciation of the element name or symbol, not the number. a 14C isotope (pronounced “c fourteen”) an 3H isotope (pronounced “aitch three”) an 15N isotope (pronounced “en fifteen”)

a carbon-14 isotope a hydrogen-3 isotope a nitrogen-15 isotope

➤ Use the symbols 2H or D for deuterium and 3H or T for tritium when no

other nuclides are present. D2O CD2H2 3H 2

CH3O3H (T2N)2CO HDSO4

2H S 2

CH2TOH 3H 2

An isotopically unmodified compound is one whose isotopic nuclides are present in the proportions that occur in nature. An isotopically modified compound has a nuclide composition that deviates measurably from that occurring in nature. An isotopically substituted compound has a composition such that all of the molecules of the compound have only the indicated nuclides at the designated positions. To indicate isotopic substitution in formulas, the nuclide symbols are incorporated into the formulas. To indicate isotopic substitution in spelled-out compound names, the number and symbol (and locants if needed) are placed in parentheses closed up to the name. N15NF2 24 NaCl H2N14CONH2 14 CH4

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UCl3 PO43– Mo(12CO)6 Na235S 32

(15N)ammonia (14C6)glucose (1,3-3H2)benzene 1-chloro(2-3H)benzene

An isotopically labeled compound is a mixture of an isotopically unmodified compound with an analogous isotopically substituted compound or compounds. Isotopically labeled compounds may be specifically labeled or selectively labeled. To indicate isotopic labeling, the number and symbol (and locants if needed) are enclosed in square brackets closed up to the compound name or formula.

specifically labeled: [14C]H4 CH2[2H2] CH3CH2[18O]H



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selectively labeled: [2H]CH4 [2H]PH3 [36Cl]SOCl2 [6,7-15N]adenosine [15N]alanine [15N]ammonium chloride [1,3-3H2]benzene

[57Co]cyanocobalamin 2,4-diamino[18O]phenol [2,8-3H]inosine [2-14C]leucine

➤ When the isotope position is specified by a group name that is part of the Downloaded by UNIV OF MINNESOTA on April 16, 2013 | http://pubs.acs.org Publication Date: June 1, 2006 | doi: 10.1021/bk-2006-STYG.ch013

parent compound, italicize the group name. [methyl-14C]toluene

➤ Isotopically labeled compounds may also be described by inserting the symbol in brackets into the name of the compound. hydrogen [36Cl]chloride [35S]sulfuric [2H]acid

➤ Do not use the left superscript within an abbreviation. [32P]CMP (not CM32P)

➤ To indicate general labeling, use the symbol G in the names of selectively

labeled compounds in which all positions of the designated element are labeled, but not necessarily in the same isotopic ratio. d-[G-14C]glucose

➤ To indicate uniform labeling, use the symbol U in the names of selectively labeled compounds in which all positions of the designated element are labeled in the same isotopic ratio. d-[U-14C]glucose

➤ When it is unknown or irrelevant whether the compound is isotopically

labeled or isotopically substituted, simply hyphenate the isotope symbol to the compound name and do not use square brackets or parentheses. 14

C-glucose H-benzene 15 N-adenosine 3

The Boughton system, used in Chemical Abstracts, does not distinguish between labeling and substitution. The isotopic variation is shown by the symbol for the isotope (with a subscript numeral to indicate the number of isotopic atoms) placed after the name or relevant portion of the name; locants are cited


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if necessary. The locants and symbols are in italics, except subscripts and Greek letters, and hyphens are used to separate them. acetamide-1-13C-15N acetic-17O2 acid benzeneacetic-carboxy,α-14C2 acid benzoic-18O acid 4-(2-propenyl-3-13C-oxy)benzoic acid toluene-methyl-14C

➤ In this system, deuterium and tritium are represented by italic lowercase letDownloaded by UNIV OF MINNESOTA on April 16, 2013 | http://pubs.acs.org Publication Date: June 1, 2006 | doi: 10.1021/bk-2006-STYG.ch013

ters d and t, respectively. acetic-t3 acid-t alanine-N,N,1-d3 ammonia-d-t ethane-1-d-2-t 1-(ethyl-2,2,2-d3)-4-(methyl-d3)benzene methan-t-ol methane-d4 tri(silyl-d3)phosphine urea-t4

Radicals ➤ In the formula of a free radical, indicate the unshared electron by a superscript or centered dot closed up to the element symbol or formula. The superscript dot comes after the symbol or formula; centered dots come before or after the symbol or formula. Br• Br• •CH3 C6H5•

H• HO• •NH2

•SH (SiH3)• •SnH3

➤ Charged radical cations and anions are often indicated by the symbol, formula, or structure with a superscript dot followed by a plus or minus sign. However, in mass spectrometry, the reverse is used. Therefore, use the order of dots and signs for charges that is appropriate for the context. (Ag2)•+ C6H5NO•3– HCO•+

R•– R2•+

R(•)(2–) (SO2) • –

mass spectrometry C3H6+• R+•



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Bonds ➤ For linear formulas in text, do not show single bonds unless the bonds are the

subject of the discussion. C6H5CH3 C6H5COOCOCH3 CH3CHOHCH3 CH3COOH H2SO4


➤ When necessary for the discussion, indicate bonds by en dashes. the –CH2– segment the C–H distances the C–C–C angle (–CH2–CH(CH3)–O–)n

➤ When necessary, show double and triple bonds in linear formulas. CH3C≡CH CH2=CH2 R–C–OH is better as RCOOH or RCO2H or RC(=O)OH

||

O

➤ Use three centered dots to indicate association of an unspecified type (e.g.,

hydrogen bonding, bond formation, or bond breaking). CPt FH–NH3 H2Oπ aromatic hydrogen bonding Mg2+O– NiAl

Crystallography Planes and Directions in Crystals ➤ Miller indices of a crystal face or a single net plane are enclosed in parentheses. (123) or (hkl) is a plane or set of planes that describe crystal faces; (h1h2h3) is a single net plane. ➤ Laue indices are not enclosed. 123 or hkl is the Bragg reflection from the set of net planes (123) or (hkl), respectively.


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➤ Indices of a set of all symmetrically equivalent crystal faces or net planes are

enclosed in braces. {hkl} is a form. ➤ Indices of a zone axis or lattice direction are enclosed in square brackets.

[123] or [uvw] is a direction.


➤ Indices of a set of symmetrically equivalent lattice directions are enclosed in angle brackets. represents all crystallographically equivalent directions of the type [uvw]. 120 1,10,1 11,0,1 1,–2,0 reflections the (111) face the (120) face the [001] axis the [010] direction the [101] direction h00 diffraction lines the hk0 zone the 002 reflection the 00l class of reflections

➤ When indices are used with spelled-out element names, separate the name of

the element and the index with a space. copper (111) rhenium (010) a gold (111) substrate on silicon (111) surfaces the silver (110) surface

➤ However, when indices are used with element symbols, close up the element

symbol to the index. Au(210) CdTe(100) Cu(111) GaAs(100) Rh(010) Si(400) an iodine-modified Ag(111) electrode the Ag(110) surface



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Types of Crystal Lattices bcc ccp fcc hcp

body-centered cubic cubic close-packed face-centered cubic hexagonal close-packed

Symmetry Operations and Structural Point Groups


➤ Use italic type for the letters in symmetry operations and structural point

groups. The symbols (Schoenflies) are as follows: E, identity; C, cyclic; D, dihedral; T, tetrahedral; O, octahedral; I, icosahedral; S, rotation–reflection; and σ, mirror plane. Align subscripts and superscripts. C1 Ci Cs C2 C 23 C 24 C∞ C2v C3v C4v C∞v

C2h C3h D2d (Vd) D3d D4d D2h (Vh) D3h D4h D∞h Ih Oh (Kh)

S3 S4 2S6 S8 σ 2σv 3σv 4σv 3σd σh Td

Crystallographic Point Groups ➤ Use arabic numerals or combinations of numerals and the italic letter m to

designate the 32 crystallographic point groups (Hermann–Mauguin). The number is the degree of the rotation, and m stands for mirror plane. Use an overbar to indicate rotation inversion. 1 m 2/m mm2

mmm 4mm 32 622

6/mmm 43m m3m

Space Groups ➤ Designate space groups by a combination of unit cell type and point group

symbol, modified to include screw axes and glide planes (Hermann–Mauguin); 230 space groups are possible. Use italic type for conventional types of unit cells (or Bravais lattices): P, primitive; I, body-centered; A, A-face-centered; B, B-facecentered; C, C-face-centered; F, all faces centered; and R, rhombohedral.


270


Pnma C2/c Pbcn I41/a Fd3m

Pnn2 P43212 Fm3m R3m Cmc21

P1 Fdd2 Aba2 I4/mmm

Crystallographic Information File


A description of the Crystallographic Information File, CIF, is included in Appendix 13-2.

Chirality ➤ Use italic type for certain chirality symbols and symmetry site terms. A C CU DD

anticlockwise clockwise cube dodecahedron

OC TP TPR TPY

octahedron trigonal phase trigonal prism trigonal pyramid

These symbols are often combined with coordination numbers and position designations for stereochemical descriptors (e.g., OC-6-11′). ➤ In chemical names, use (R) and (S), with designated locants when applicable, as prefixes to designate absolute configuration. (R)-hydroxyphenylacetic acid (S)-2,3-dihydroxypropanoic acid (1S,2S,4R)-trichloro-1,2,4-trimethylcyclohexane

➤ Indicate optical rotation by plus and minus signs in parentheses and hyphen-

ate them to the chemical name. (±)-4-(2-aminopropyl)phenol (+)-glucose (–)-tartaric acid

➤ Use small capital letters d and l for absolute configuration with amino acids and carbohydrates. β-d-cellotetraose d-allothreonine d-glucose d-valine dl-leucine hydroxy-dl-glutamic acid

5-hydroxy-l-lysine hydroxy-l-proline l-alanine l-alloisoleucine l-ascorbic acid l-phenylalanine



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271

➤ Use a hyphen between (+) or (–) and d or l. (–)-d-fructose (–)-d-glyceraldehyde (+)-l-phosphoglycerol

Concentration ➤ Use square brackets enclosing an element symbol or formula to indicate its


concentration in reactions and equations, but not in narrative text.

correct [Mg2+] = 3×10–2 M The Mg concentration decreased with repeated washings.

incorrect The [Mg] was found to be greater in the unwashed samples.

➤ Do not use square brackets to indicate concentration with a spelled-out

name. [Ca2+] (not [calcium]) [NaCl] (not [sodium chloride])

➤ Do not use italic type for the chemical concentration unit M (molar, moles

per cubic decimeter, moles per liter) or the unit N (normal). Use italic type for the unit m (molal, moles per kilogram). Use a space between the number and these abbreviations, that is, on each side of these abbreviations. 8 M urea 1 mM EDTA 6 N HCl 2.0 m NaOH

➤ When concentration is given as percentage, use the percent sign closed up to

the number. 20% H2SO4 90% acetonitrile/10% water

➤ Generally, the negative logarithm of the hydrogen ion concentration is

denoted by pH; the negative logarithm of the hydroxide ion concentration is denoted by pOH. Use a space to separate pH or pOH and the number. Use


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roman type for pH and pOH; always use lowercase for “p”; always capitalize “H” and “OH”. Solutions were titrated to pH >11. The UV spectra were measured at pH 6. A pOH of

Conventions in Chemistry - The ACS Style Guide (ACS Publications)

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