Atoms, Elements & Compounds

Activities to try

1. 1

   Atom workshop: build and classify

   Why it works: Element, compound and mixture are distinguished by how atoms are arranged: one kind of atom (element), different kinds chemically joined in a fixed ratio (compound), or substances merely together and separable (mixture). A formula records how many of each atom are joined.

   1. Drag atoms from a palette and snap identical atoms together (e.g. two blue atoms) a2014 observe the classifier label the result 'element'.
   2. Snap different atoms together (e.g. two blue + one red) and watch a formula box write the compound's formula while the classifier flips to 'compound'.
   3. Scatter a jumble of two or more DIFFERENT kinds of separate particles that are not joined to each other (e.g. some blue–blue molecules alongside some separate red atoms) and observe the classifier read 'mixture'; note that a jumble of identical molecules is still one pure substance, not a mixture.
   4. Use a 'try to separate' tool: pull a mixture cleanly into its parts, then try the same on a compound and find it cannot be pulled apart physically.
   5. State in your own words why the built thing is an element, a compound, or a mixture, and read the formula off your model as a count of each kind of atom.
2. 2

   New properties: a compound is not its elements

   Why it works: When elements chemically combine into a compound, the compound has genuinely new properties, unlike a mixture where each component keeps its own properties and can be separated physically.

   1. Compare the properties of reactive sodium metal and poisonous chlorine gas, then observe (via demonstration or described reaction) that combined they form ordinary edible table salt (NaCl).
   2. State what changed: the compound has its OWN properties, different from both elements.
   3. Predict for iron filings mixed with sulfur powder: can a magnet still pull out the iron, and does it still look like iron + sulfur? (Yes a2014 it is a mixture; each part keeps its own properties.)
   4. Then consider a fresh portion heated to form dark grey iron sulfide and predict whether the magnet still pulls out iron (No, if all the iron has reacted: a new compound has formed. In real demonstrations leftover unreacted iron may still be attracted, so any pull comes from leftover iron, not from the compound).
   5. Explain the difference between the two iron/sulfur results in terms of 'just together' versus 'chemically joined'.
3. 3

   Atom structure and symbol reference

   Why it works: Atoms have internal structure a2014 a central nucleus of protons and neutrons with electrons arranged in shells around it a2014 and chemical symbols are a shorthand; a formula names the elements present and the number of atoms of each. Detailed electron arrangement is kept light at this stage.

   1. Explore a labelled atom diagram showing a tiny central nucleus a2014 containing protons and neutrons a2014 with electrons arranged around it in shells, together with the element's chemical symbol (the electron-shell detail is kept light at this stage).
   2. Match chemical symbols to their elements using a symbol key.
   3. Read given formulae (e.g. H2O, CO2, NaCl) aloud, naming each element and how many atoms of each are present (for NaCl, which is not made of separate molecules, read the formula as a 1:1 ratio of sodium to chlorine).
   4. Decide for each example whether it is an element or a compound and justify it.