In Depth: Atomic Mass Units

The video tutorial explains the concept of atomic mass, focusing on the relative isotopic mass. It uses helium as an example to introduce the idea of mass number and atomic mass. The tutorial discusses the standardization of atomic mass using carbon-12 as a reference, explaining that one atomic mass unit is 1/12 of the mass of a carbon-12 atom. Examples of atomic masses for helium, hydrogen, and fluorine are provided. An exercise on calculating the atomic mass of nitrogen is included. The video concludes with a discussion on why not all atomic masses are whole numbers, setting the stage for a future lesson.

What is the mass number of a helium atom?

• 8

• 4

• 2

• 6

Which element is used as the standard reference for atomic mass units?

• Hydrogen

• Oxygen-16

• Carbon-12

• Helium

How is one atomic mass unit (amu) defined?

• 1/16 of the mass of an oxygen atom

• 1/4 of the mass of a helium atom

• 1/12 of the mass of a carbon-12 atom

• 1/10 of the mass of a hydrogen atom

What is the relative isotopic mass of a hydrogen atom?

• 4

• 2

• 1

• 12

What is the mass number of nitrogen?

• 12

• 18

• 14

• 16