Someone

atElement = element[]
element[0] = 'H_'
element[1] = 'He'
element[2] = 'Li'
element[3] = 'Be'
element[4] = 'B_'
element[5] = 'C_' 
element[6] = 'N_' 
element[7] = 'O_'
element[8] = 'F_'
element[9] = 'Ne'
element[10] = 'Na'
element[11] = 'Mg'
element[12] = 'Al'
element[13] = 'Si'
element[14] = 'P_'
element[15] = 'S_'
element[16] = 'Cl'
element[17] = 'Ar'
element[18] = 'K_'
element[19] = 'Ca'

for i in range(0,19):
	print atElement[i]
	i=i+1