Unit 02 · Atoms, Elements & the Periodic Table
Everything around you is built from atoms — tiny building blocks far too small to ever see. This unit sorts matter by what it’s made of: an element is one kind of atom, a compound is elements joined together, and a mixture is just different things stirred together and never truly combined. Then it opens the periodic table, the big chart that arranges the elements into rows and columns, metals on one side and nonmetals on the other. Mastery means you can tell an element, a compound, and a mixture apart — and separate a mixture using a physical property.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Atoms as building blocks | Thinks atoms are alive or can be seen with a hand lens. | Knows atoms are tiny but cannot say what they build. | Describes atoms as the tiny building blocks of all matter, far too small to see, and names them as what every element is made of. |
| Elements, compounds & mixtures | Treats every sample as the same kind of thing. | Defines an element but mixes up compounds and mixtures. | Tells an element, a compound, and a mixture apart and gives an everyday example of each. |
| Reading the periodic table | Sees the table as a random grid of boxes. | Finds an element by its symbol but cannot use rows or columns. | Reads the table by periods (rows) and groups (columns) and explains what elements in the same group share. |
| Metals vs. nonmetals | Cannot say where metals sit on the table. | Points to the metals but cannot name a property that sets them apart. | Locates metals and nonmetals on the table and describes how their properties differ. |
| Lab technique (separating a mixture) | Mixes samples together and cannot recover them. | Separates part of a mixture but loses material along the way. | Separates a mixture cleanly — by filtering, a magnet, or evaporation — and explains the physical property that made it possible. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“Salt water is a mixture — the salt is just dissolved in the water, not combined with it — so I boiled the water off and the salt was left behind in the dish. Salt itself is a compound, and so is water; each one is built from atoms far too small to ever see.”
“Salt water is a compound because it has two things in it. I don’t think you can get the salt back out of it.”
You demonstrate this unit hands-on — separating a real mixture and sorting samples into element, compound, and mixture — plus short oral checks where you explain your reasoning aloud, not a multiple-choice test. A criterion counts as mastered only when you can both do the separation and explain what the periodic table or the property tells you. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.