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Mendeleev example
Oxygen: bonding and reactivity
Oxygen's electron structure supports strong bonding and many oxidation reactions.
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.