Why is deuterium oxide called " heavy water"?

Question

Is it because it has extra hydrogen atoms?

Answer 1

Deuterium oxide is commonly called "heavy water" because it contains a heavier isotope of hydrogen called deuterium. Deuterium is an isotope of hydrogen that has an extra neutron, making it twice as heavy as the regular hydrogen isotope, which is called protium.

Since deuterium is heavier than protium, water molecules containing deuterium instead of protium have a slightly higher mass, giving them a greater density than ordinary water. This increased density is what gives it the name "heavy water". It is important to note that heavy water is not significantly thicker or denser than regular water in a way that can be noticed by humans.