Question

Element ,Atomic number,Mass number, Electrone distribution, velocity .table 20

Answer 1

Hydrogen1 H 1Helium4 He 2Lithium7 Li 3Beryllium9 Be 4Boron11 B 5Carbon12 C 6Nitrogen14 N 7Oxygen16 O 8Fluorine19 F 9Neon20 Ne 10Sodium23 Na 11Magnesium24 Mg 12Aluminium27 Al 13Silicon28 Si 14Phosphorus31 P 15Sulphur32 S 16Chlorine35.5 ClArgon40 Ar 18Potassium39 K 19Calcium40 Ca 20
I hope it's help u

Answer 2

the answer is on the top and other two elements are potassium and calcium
atomic number of potassium is 19,2,8,9.
calcium is 20,2,8,8,1,40