Final answer:
Numbers greater than 7 on the pH scale indicate a basic (alkaline) solution, characterized by a low hydronium ion concentration and a high hydroxide ion concentration.
Step-by-step explanation:
On the pH scale, numbers greater than 7 indicate a basic (alkaline) solution. The pH scale ranges from 0 to 14 and describes the acidity or basicity of a solution. A solution with pH less than 7 is considered acidic, a pH of 7 is neutral, and a pH greater than 7 is basic.
A basic solution has a hydroxide ion molarity greater than 1.0 × 10-7 M, which also means it has a hydronium ion molarity less than 1.0 × 10-7 M. This relationship helps us quickly determine the nature of the solution. For example, household ammonia is a common basic solution with a pH above 7.