Atomic Number
Atomic number is the number of protons present in the nucleus of an atom.
Practice This ConceptMain explanation
Teacher explanation
Atomic number is represented by Z. It identifies the element because each element has a fixed number of protons. In a neutral atom, the atomic number also equals the number of electrons, but the main identity of the element depends on protons.
Example
Carbon has atomic number 6, so every carbon atom has 6 protons.
Simple analogy
Atomic number is the element's proton ID card.
Common confusion
Students sometimes say atomic number is protons plus neutrons, which is actually mass number.
Exam tip
If the question asks identity of an element, look at proton number or atomic number.
Answer writing and exam use
1-mark use
Write the exact meaning of atomic number in one clean line.
2-mark use
Define atomic number and add one example or condition.
3-mark use
Explain atomic number, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
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