H2O
Mendeleev example
Water: why shape matters
Water is bent, so its bond dipoles do not cancel. Geometry helps explain polarity.
Mendeleev
Start with the particle story: which protons, electrons or nuclei are changing? Then connect that story to the property you observe.
1
Identify the particles or structure involved.
2
Predict the direction of the effect.
3
Check the explanation against the periodic table or a measured property.