Chemistry Basics

General Science · 5 min read · Sunitha Rao

Atoms, common compounds and everyday chemical names.

An atom has protons and neutrons in its nucleus with electrons around it. The atomic number is the proton count and decides the element; the mass number is protons plus neutrons.

Exams love the common names of compounds. Common salt is NaCl, baking soda is sodium bicarbonate, washing soda is sodium carbonate, quicklime is calcium oxide and marble is calcium carbonate.

Acids taste sour and turn blue litmus red; bases taste bitter and turn red litmus blue. On the pH scale 7 is neutral, below 7 acidic and above 7 basic.

Important points

  • Atomic number = number of protons.
  • Common salt is sodium chloride, NaCl.
  • Baking soda is NaHCO3; washing soda is Na2CO3.
  • pH 7 is neutral, below 7 acidic, above 7 basic.
  • Water has the formula H2O.

Examples

  1. Vinegar is dilute acetic acid, so it turns blue litmus red.
  2. Lime water turns milky with CO2 because calcium carbonate forms.

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