A halide is the salt formed when a halogen combines with a metal, such as potassium bromide; the halide ion is the negative ion a halogen forms, such as Cl⁻.
A halide is the salt formed when a halogen combines with a metal, such as potassium bromide; the halide ion is the negative ion a halogen forms, such as Cl⁻. Malay: halida · Chinese: 卤化物.
A halide is what a halogen becomes once it has gained its extra electron. Each halogen atom has seven valence electrons and needs one more for a stable octet, so when it reacts with a metal it takes an electron from that metal and turns into an ion with a charge of −1. The names follow a simple pattern: chlorine gives chloride (Cl⁻), bromine gives bromide (Br⁻) and iodine gives iodide (I⁻), and the metal comes first in the salt’s name, as in sodium chloride or potassium bromide. Many halides are soluble, colourless salts, and they turn up throughout chemistry, common table salt is itself the halide sodium chloride.
Example. When sodium reacts with chlorine, the sodium loses one electron and the chlorine gains it, giving sodium chloride, NaCl, which is an ionic salt made of Na⁺ and Cl⁻. In a displacement reaction, the halide in solution, the bromide ions of potassium bromide, say, is the starting material from which a more reactive halogen sets the free halogen loose.
Confusion to avoid. Keep “halogen” and “halide” clearly apart: the halogen is the reactive element (chlorine, Cl₂), and the halide is the salt or negative ion formed from it (chloride, Cl⁻). The two words look alike, and swapping them is a common slip that costs marks.
In the Periodic Table of Elements chapter the halide is the product side of halogen chemistry, and it links this chapter forward to bonding, where forming a halide ion is a classic example of an atom reaching a stable octet.
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