electro-

Quick Definition

Meaning: Electricity or electric charge

Origin: Greek (elektron = amber)

Pronunciation: ee-LEK-troh

Why It Matters

The prefix electro- signals that electricity or electric charge is involved. In chemistry, it appears most prominently in electrochemistry — the study of chemical processes that involve electron transfer. The most important term is electrolysis, which uses electrical energy to drive a non-spontaneous reaction. This is the opposite of a galvanic cell (like a battery), which uses a spontaneous chemical reaction to generate electricity. Students frequently mix these up. Here's the rule: electrolysis requires external power (you plug it in), while a galvanic cell produces power (you put it in a device). Both involve oxidation at the anode and reduction at the cathode, but the signs are reversed. In electrolysis, the anode is positive (because it's connected to the positive terminal of the power source), while in a galvanic cell, the anode is negative. This sign convention is a classic exam trap. The word 'electrolyte' also derives from this prefix: an electrolyte is a substance that conducts electricity when dissolved in water because it dissociates into ions. Not all solutions conduct electricity — pure water is a poor conductor, but salt water is an excellent one. When you see electro-, think 'electrons are moving.'

Examples

• Electrolysis
• Electrolyte
• Electronegativity
• Electroplating

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