Here's a breakdown:
* Atoms: The basic building blocks of matter, composed of protons, neutrons, and electrons.
* Element: A substance made up of only one type of atom, defined by its number of protons (atomic number).
* Isotopes: Atoms of the same element that have the same number of protons but different numbers of neutrons.
Since neutrons have mass, isotopes of the same element differ in their atomic mass. This is because the mass of an atom is primarily determined by the number of protons and neutrons in its nucleus.
Example:
* Carbon-12 (¹²C) has 6 protons and 6 neutrons.
* Carbon-14 (¹⁴C) has 6 protons and 8 neutrons.
Both are carbon atoms, but ¹⁴C is heavier due to the extra neutrons.
Key Points:
* Atomic number determines the element.
* Mass number (number of protons + neutrons) determines the isotope.
* The presence of isotopes explains why the atomic mass of an element on the periodic table is not a whole number. It's an average of the masses of all naturally occurring isotopes of that element.
In conclusion, the variation in neutron count within isotopes of the same element leads to different atomic masses, even though the elements themselves are defined by their consistent number of protons.
