Practice Atomic Number in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The number of protons in an atom's nucleus, which uniquely identifies the element.

The atom's ID number — Z = 6 always means carbon, no matter what else changes.

Example 1

easy
Element X has 15 protons. Identify the element and determine the number of electrons in a neutral atom.

Example 2

medium
Two atoms both have a mass number of 40. Atom A has 20 protons and Atom B has 19 protons. Are they the same element? How many neutrons does each have?

Example 3

easy
What is the atomic number of an element with 29 protons? Name the element.

Example 4

easy
An atom has atomic number 15. How many protons does it have? If the atom is neutral, how many electrons does it have?
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