give me a list of atomicity of all elements

At this level, you do not require the atomicity of all the elements. There are more than 100 elements present in the periodic table. Learning about all of them at this stage would be difficult. You will learn more about them in your higher grades the important one are given below.
 

Element	Symbol of molecule	Number of atoms in one molecule (atomicity)
Hydrogen	H2	2
Nitrogen	N2	2
Oxygen	O2	2
Flourine	F2	2
Chlorine	Cl2	2
Bromine	Br2	2
Iodine	I2	2
Ozone	O3	3
Phosphorus	P4	4
Sulphur	S8	8

Note: The atomicity of noble gases is 1 i.e. they are monoatomic.