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🧪Halogen vs Noble gas💡

Groups 17 and 18 are neighbors with opposite chemistry. One craves an electron, the other already has a full shell.

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🧪Halogen
  • Group 17, seven valence electrons
  • Highly reactive nonmetals
  • Gains one electron to form -1 ions
  • Forms salts with metals (halides)
  • Examples: fluorine, chlorine, iodine
💡Noble gas
  • Group 18, full valence shell
  • Inert and almost unreactive
  • Does not normally form ions
  • Exists as single, stable atoms
  • Examples: helium, neon, argon

Verdict

Halogens are one electron short of stability and so are very reactive; noble gases are already complete and almost inert. They sit one column apart for that reason.

Frequently asked

Why are noble gases unreactive?+

Their outer electron shell is already full, so they have no drive to gain, lose or share electrons.

Why are halogens so reactive?+

They need just one more electron to fill their shell, making them eager to react.

What ion do halogens form?+

Halogens gain one electron to form -1 anions called halides.

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