2. Trong một pin điện, vật chất nào đi từ cực âm đến cực dương? a) Các electron b) Nguyên tử c) Ion d) Phản ứng

a) Các electron

Explanation:

In a battery, chemical reactions occur at the electrodes (anode - negative terminal, and cathode - positive terminal) and in the electrolyte.

At the anode (negative terminal): A material (like zinc in a typical alkaline battery) undergoes oxidation, releasing electrons.
The electrons then flow through the external circuit (the wire connected to the battery) because they are repelled by the negative terminal and attracted to the positive terminal.
At the cathode (positive terminal): Another chemical reaction occurs where a material (like manganese dioxide in an alkaline battery) accepts these electrons.
While ions move within the electrolyte solution inside the battery to balance the charge, it is the electrons that flow through the external circuit from the negative terminal (anode) to the positive terminal (cathode) to power a device.

Therefore, the correct answer is a) Các electron.