Answers

2014-05-15T14:08:27+05:30
They are group of elements. Most of the lanthanides and actinides are radioactive.
Halogens are a group of non metals with valency -1.
halogen means salt makers. They combine with metals or metal like radicals to form salts (eg, Nacl, BaCl₂, NH₄Cl). They also combine with hydrogen to form acids (eg, HCl, HBr, HF etc). The halogens are toxic. Their toxicity decreases with increase in weight. The halogens are Fluorine(F), Chlorine(Cl), Bromine(Br), Iodine(I), Astatine(At), and artificially created element 117 called Ununseptium(Uus).  
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2014-05-15T14:32:18+05:30
Lanthanides and actinides are present below in the periodic table.they are called as inner transition elements because there is no place for them in d-block,hence they placed at below and named as f-block elements.lanthanides start from cerium and actinides start from thorium.
Halogens are seventh A group elements in the periodic table.they are flourine(F),chlorine(Cl),bromine(Br),iodine(I),astatine(At).they are called halogens because they salt forming compounds.
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