These slightly different atoms of the same chemical element are called isotopes of that element.
Deep inside the Inner Gorge of Grand Canyon, northern Arizona, are the crystalline basement rocks that probably date back even to the Creation Week itself.
Orbiting around the nucleus are electrons (tiny particles each with a single electric charge).
The atoms in each chemical element may vary slightly in the numbers of neutrons within their nuclei.
Among these metamorphosed volcanic strata are amphibolites, belonging to the Brahma Schist.
There's a small amount of radioactive carbon-14 in all living organisms.
The universe is full of naturally occurring radioactive elements.
Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms." When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
So in order to date most older fossils, scientists look for layers of igneous rock or volcanic ash above and below the fossil.
Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium.