U1: Atomic Structures and Properties

Atomic Mass Unit (AMU or U)

Measures mass at an atomic scale, because atoms are super small.

Protons and Neutron’s Effect on Atomic Mass

Protons and Neutrons weigh way more than electrons, approximately 1 amu (or u), so you can use the number of protons and neutrons in an element to find its atomic mass.

Isotope

Different version of an element with same number of protons but different number of neutrons.

Atomic Number

The number assigned to an element on the periodic table, equal to the number of protons found in an atom of that element.

Avogadro’s Constant

6.02214076 × 10²³. Often abreviated to 6.022 × 10²³.

Mole

6.022 × 10²³. of something, a unit of measurement.

Imagine it like saying a dozen of something. If you have a dozen Hydrogen atoms, you have 12 hydrogen atoms. If you have a ____ of hydrogen atoms, you have 6.022 × 10²³ hydrogen atoms.

If 1 atom weighs 6.94 u, then:

• 6.022 × 10²³ atoms of lithium (1 mole of lithium) will weigh 6.94 grams

Isotope

A different version of an element with the same # of protons but a different number of neutrons.