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Naming Compounds and Writing Chemical Equations

Atomic structure and the periodic table • Atomic models and isotopes

Key concepts

What you'll likely be quizzed about

  • Element symbols consist of one or two letters, often derived from the element name.
  • Chemical formulae show the quantity and type of atoms in a substance.
  • Subscripts indicate the number of atoms of an element in a molecule; for example, H2O represents two hydrogen atoms and one oxygen atom.
  • The absence of a subscript indicates one atom.
  • Ionic compounds display the simplest ion ratio that balances overall charge.

Flashcards

Test your knowledge with interactive flashcards

What does a subscript in a formula indicate?

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A subscript shows the total number of atoms of that element in one molecule.

Key notes

Important points to keep in mind

Identify bonding types before writing formulae.

Balance equations using coefficients, never change subscripts.

Use correct ion charges to find ionic formulae via charge cancellation.

Apply -ide ending for simple anions and use established names for polyatomic ions.

Include state symbols to specify the physical states of reactants and products.

Ensure equal atom counts of each element on both sides after balancing.

Oxygen typically appears as O2 in its elemental gaseous form in equations.

Simplify coefficients to the smallest whole-number ratio after balancing.

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