Explain the existence of isotopes using different neutron numbers.

In the subtopic Mass number, isotopes and mass spectrometry, this AQA A-Level Chemistry 7405 learning objective focuses on explain the existence of isotopes using different neutron numbers. It belongs to Atomic structure, so revision should stay anchored to this exact subtopic rather than drifting into a generic GCSE-level chemistry summary. Approved keywords to use include isotope. Neutron number. means the number of neutrons in an atom's nucleus, which contributes to the mass number of the isotope Avoid the mistake of students often confuse isotopes with ions, thinking they are the same because both involve variations of atoms; instead, remember that isotopes have the same number of protons but different numbers of neutrons, while ions are atoms that have gained or lost electrons, resulting in a charge. For example, Carbon-12 and Carbon-14 are isotopes of carbon, while Na+ is a sodium ion For exam answers, remember that isotopes of an element have the same number of protons but different numbers of neutrons. This is crucial for explaining their existence