Chemistry reference data
Chemical elements, compounds, and reactions.
Topic guide
What Chemistry covers
Chemistry reference data covers the periodic table and the ways atoms combine: chemical bonds, common acids and bases and the pH scale that measures them, and the functional groups that organize organic chemistry. The facts are well established, but they come with conventions that matter, such as how atomic mass is defined, which indicator colors are used for pH, and that many acid and base strengths depend on concentration and solvent. Safety information, such as handling strong acids, belongs alongside the properties.
Key ideas
- Atomic number and mass
- The atomic number counts protons and defines the element; atomic mass is a weighted average over isotopes, so it is not a whole number.
- Bond types
- Ionic bonds transfer electrons, covalent bonds share them, metallic bonds pool them. Real bonds sit on a spectrum of polarity.
- Intermolecular forces
- Weaker attractions between molecules (hydrogen bonds, dipole-dipole, London dispersion) that govern boiling points and solubility.
- pH
- The negative base-10 logarithm of hydrogen-ion activity. Each unit is a tenfold change; 7 is neutral at 25 degrees Celsius.
- Strong vs weak
- A strong acid or base dissociates almost completely in water; a weak one only partly. Strength is not the same as concentration or danger.
- Functional group
- A characteristic group of atoms that determines how an organic molecule reacts, such as an alcohol or a carboxylic acid.
- Indicator
- A substance that changes color with pH. Each indicator changes over its own range, so colors differ between indicators.
Common pitfalls
- Assuming a low pH always means a strong acid. A dilute strong acid and a concentrated weak acid can have similar pH.
- Taking indicator colors as universal; the colors listed depend on the indicator used.
- Treating atomic masses as exact integers. They are averages and are revised slightly as measurements improve.
- Mixing chemicals from a reference list without the safety data; some combinations release toxic gas or heat.
Using it from an agent
- When asked how to dilute or mix acids and bases, include the safety rule (add acid to water, wear eye protection) and suggest consulting a safety data sheet.
- Give formulas with correct subscripts and state the temperature when quoting pH or pKa values.
- Use the periodic-table dataset for symbols and masses, and say that it covers only the first thirty elements.
Start with: Periodic Table First 30 Elements · pH Scale and Indicators
Datasets in Chemistry
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Chemical Bond Types
Primary types of chemical bonds and interactions.
11 entries -
Common Acids and Bases
Frequently encountered acids and bases with formulas.
18 entries -
Organic Functional Groups
Common functional groups in organic chemistry.
18 entries -
Periodic Table First 30 Elements
Atomic data for the first thirty chemical elements.
30 entries -
pH Scale and Indicators
pH ranges and common indicator color changes.
14 entries
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