UP:SC15.CHM.2

Students know:

Each atom has a charge substructure that consists of a nucleus, which is made of protons and neutrons, surrounded by electrons.
The majority of an atom's mass comes from the protons and neutrons in the nucleus.
Electrons have a very small mass, so they are not typically included in atomic mass calculations.
Atoms of an element can have different masses, and we call those atoms isotopes.
Isotopes of a given element have the same number of protons, but different number of neutrons.
Most elements exist in nature in isotopic form.

Students are able to:

Develop a model based on evidence to illustrate the relationship between the structure of the atom and the average atomic mass of an element.
Use the model to make predictions.
Calculate weighted averages.
Determine the most common isotopic form of an element in nature.

Students understand that:

Models can be computational or mathematical.
The published atomic mass of an element is a weighted average of all known isotopes of that element.
Macroscopic patterns are related to the nature of atomic/ molecular/ particulate level structure.

Developing and Using Models

Scale, Proportion, and Quantity