User:Double sharp/Halogen

Halogens
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson chalcogens ←    → noble gases
IUPAC group number 17 Name by element fluorine group Trivial name halogens CAS group number (US, pattern A-B-A) VIIA old IUPAC number (Europe, pattern A-B) VIIB
↓ Period
2	Fluorine (F) 9 Halogen
3	Chlorine (Cl) 17 Halogen
4	Bromine (Br) 35 Halogen
5	Iodine (I) 53 Halogen
6	Astatine (At) 85 Halogen
7	Tennessine (Ts) 117 Halogen
Legend primordial element element from decay Synthetic Atomic number color: black=solid, green=liquid, red=gas

The halogens are a group (column) in the periodic table consisting of the chemical elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and possibly also the synthetic element tennessine (Ts). This group lies in the p-block of the periodic table of elements as all halogens have seven valence electrons, arranged in the electron configuration ns²np⁵. Since all the halogens are one electron short of a full octet, they exhibit well-characterised homologous behaviour and provide one of the the best examples of group trends in properties in the periodic table.

In their standard states, the halogens are all quite volatile

say something about diatomicity (sharing)

Oh dear I've gotten myself stuck into the astatine problem again, haven't I? I think I need to take care of occurrence in the first paragraph so I can mention that At is rare because it's so radioactive so a negligible amount accumulates from U decay (and Ts is even more ephemeral, but has no naturally occurring parent). Then we can sya that not much is known about it