Question

from atomic number 1 to 20 and which one is metal or non-metal which form positive ions and negative and write down
the valency of each atom with reason

Answer 1

atomic no 17 is non metals and valency 1

Answer 2

atomic number 1 that is hydrogen...
is A gas element bt recently under very high pressure hydrogen was observed in highly dense form in solid state as well .nd proved very good conducter... an an elctro positive element.
besides ds... u can clasify elements based on there properties..
s block ... metal elements.. atomic number includes u mentiones 1. 3. 4. 11. 12. 19. 20ie hydrogen. lithium berylium sodium magnessium potassium and calcium respectively. these are electro positive wd there velency 1 in case of hydrogen. lithium and sodium. potassium nd 2 in case of berylium and magnessium. calcium
rest all elements excluding above mentioned elements are non metal elements upto atomic number 20. Helium.2 neon.10 and argon 18 are gasious elements wd zero velency. called as inert elements.