s-block
periodic table block
hydrogen
chemical element with symbol H and atomic number 1
francium
chemical element with symbol Fr and atomic number 87
helium
chemical element with symbol He and atomic number 2; rare gas
potassium
chemical element with symbol K and atomic number 19
rubidium
chemical element with symbol Rb and atomic number 37
caesium
chemical element with symbol Cs and atomic number 55
lithium
chemical element with symbol Li and atomic number 3
sodium
chemical element with symbol Na and atomic number 11