# Develop and use models to illustrate the structure of atoms, including the subatomic particles with

### Disciplinary Core Idea

PS1: Matter and Its Interactions

A student has been learning about atoms. He wrote a small paragraph describing one.

How an Atom Looks

An atom looks similar to a racetrack. There are small particles that move like cars on a racetrack. These particles move in a circle around the center of the track and do not easily move away from the center.

The student describes particles on the edge of the atom. Which statement supports the student’s claim that the particles on the edge of the atom do not move away from the center?

 Standard Text and Component Idea Explanation and Support of Standard Crosscutting Concept Science and Engineering Practice 7.PS1.1 Develop and use models to illustrate the structure of atoms, including the subatomic particles with their relative positions and charges. Component Idea: A. Structure and Properties of Matter Models should include a nucleus containing positively charged protons and neutrons without charge. Students should recognize that electrons are located outside of the nucleus, but are not responsible for creating models for the distribution of all electrons, nor are they expected to list full configurations for electrons. These ideas may still be desirable to lead students to an understanding of valence electrons.  Students should see the relationship between the number of valence electrons possessed by an element and its location on the periodic table. Student should connect the components of their models (protons, neutrons, electrons) to arrangement of the periodic table. Models including locations and charges of subatomic particles are sufficient to explain relative sizes of atoms (the force of protons on electrons).  These same discussions of atomic radius can extend into the general electronegativity trends, arising from repulsion of electrons as they are condensed in smaller radii. The idea of high electronegativity combining with low electronegativity will support patterns observable in way elements combine on the periodic table (7.PS1.5). (Discussions of valence electrons should be limited to elements with only one common oxidation state, and only those with valence electrons in S and P orbitals.) Scale, Proportion, and Quantity Students develop models to investigate scales that are beyond normal experiences. Developing and using models Students create models which are responsive and incorporate features that are not visible in the natural world, but have implications on the behavior of the modeled systems and can identify limitations of their models.