diff --git a/src/keywords.F90 b/src/keywords.F90
index 48b7927..46d3288 100644
--- a/src/keywords.F90
+++ b/src/keywords.F90
@@ -23,6 +23,7 @@ MODULE keywords
 
 
     use iso_fortran_env
+    use periodic_table, only: atom_t, element    
 
     implicit none
 
diff --git a/src/periodic_table_m.f90 b/src/periodic_table_m.f90
index a322ed7..bbfb299 100644
--- a/src/periodic_table_m.f90
+++ b/src/periodic_table_m.f90
@@ -1,12 +1,30 @@
-module periodic_table
+! Enter licence information here
 
+
+! Licence information ends here
+!
+! Note. The elemental data is taken from the NIST website (https://physics.nist.gov/PhysRefData/Handbook/periodictable_a.htm)
+!       The data tabulated in this file is only for the most abundant isotope only.
+
+module periodic_table
     public :: element, atom_t
+    private :: i1, sp
+
+    integer, parameter :: sp = kind(1.0)
+    integer, parameter :: i1 = kind(int1)
 
     type :: atom_t
-        character(len=20)        :: name
-        character(len=3)        :: symbol        
-        integer                 :: znuclear
-        real                    :: atomic_mass
+        real(kind=sp)        :: atomic_mass  ! in amu
+        character(len=20)    :: name
+        character(len=3)     :: symbol        
+        integer(kind=i1)     :: znuclear
+        integer(kind=i1)     :: isotope = 1  ! currently supports only the most abundant
+!   future plans
+!                               covalent_radii        
+!                               ground state term symbol
+!                               total spin
+!                               magnetic moment        
+
     end type atom_t
 
     contains 
@@ -17,9 +35,79 @@ module periodic_table
 
     select case(sym)
         case("hydrogen", "Hydrogen", "H", "1")
-                atom = atom_t(name="hydrogen", symbol="H", atomic_mass=1.00794, znuclear=1)
+
+            atom = atom_t(name="hydrogen",  symbol="H",     atomic_mass=1.007825,   znuclear=1)
+
+        case("helium", "Helium", "He", "2")
+
+            atom = atom_t(name="helium",    symbol="He",    atomic_mass=4.00260,    znuclear=2)
+
+        case("lithium", "Lithium", "Li", "3")
+
+            atom = atom_t(name="lithium",   symbol="Li",    atomic_mass=7.016003,   znuclear=3)
+
+        case("beryllium", "Beryllium", "Be", "4")
+
+            atom = atom_t(name="beryllium", symbol="Be",    atomic_mass=9.012182,   znuclear=4)
+
+        case("boron", "Boron", "B", "5")
+
+            atom = atom_t(name="boron",     symbol="B",     atomic_mass=11.009305,  znuclear=5)
+
+        case("carbon", "Carbon", "C", "6")
+
+            atom = atom_t(name="carbon",    symbol="C",     atomic_mass=12.000000,  znuclear=6)
+
+        case("nitrogen", "Nitrogen", "N", "7")
+
+            atom = atom_t(name="nitrogen",  symbol="N",     atomic_mass=14.003074,  znuclear=7)
+
+        case("oxygen", "Oxygen", "O", "8")
+
+            atom = atom_t(name="oxygen",    symbol="O",     atomic_mass=15.994915,  znuclear=8)
+
+        case("fluorine", "Fluorine", "F", "9")
+
+            atom = atom_t(name="fluorine",  symbol="F",     atomic_mass=18.9984032, znuclear=9)
+
+        case("neon", "Neon", "Ne", "10")
+
+            atom = atom_t(name="neon",      symbol="Ne",    atomic_mass=19.992435,  znuclear=10)
+
+        case("sodium", "Sodium", "Na", "11")
+
+            atom = atom_t(name="sodium",    symbol="Na",    atomic_mass=22.989767,  znuclear=11)
+
+        case("magnesium", "Magnesium", "Mg", "12")
+
+            atom = atom_t(name="magnesium", symbol="Mg",    atomic_mass=23.985042,  znuclear=12)
+
+        case("aluminum", "Aluminum", "aluminium", "Aluminium", "Al", "13")
+
+            atom = atom_t(name="aluminum",  symbol="Al",    atomic_mass=26.981540,  znuclear=13)
+
+        case("silicon", "Silicon", "Si", "14")
+
+            atom = atom_t(name="silicon",   symbol="Si",    atomic_mass=27.976927,  znuclear=14)
+
+        case("phosphorus", "Phosphorus", "P", "15")
+
+            atom = atom_t(name="phosphorus",symbol="P",     atomic_mass=30.973762,  znuclear=15)
+
+        case("sulfur", "Sulfur", "sulphur", "Sulphur", "S", "16")
+
+            atom = atom_t(name="sulfur",    symbol="S",     atomic_mass=31.972070,  znuclear=16)
+
+        case("chlorine", "Chlorine", "Cl", "17")
+
+            atom = atom_t(name="chlorine",  symbol="Cl",    atomic_mass=34.968852,  znuclear=17)
+
+        case("argon", "Argon", "Ar", "18")
+
+            atom = atom_t(name="argon",     symbol="Ar",    atomic_mass=39.962384,  znuclear=18)
+                
         case default
-                error stop "Unknown element or symbol"
+                error stop "Unknown element's atomic number or symbol"
     end select
     return 
     end function      
diff --git a/src/trial.f90 b/src/trial.f90
index 8138af9..6e68a18 100644
--- a/src/trial.f90
+++ b/src/trial.f90
@@ -9,7 +9,7 @@ program trial_reading
 
         type(atom_t) :: atom1
 
-        atom1 = element("Hydrogen")
+        atom1 = element("sulfur")
 
         print*, "atom info name ", atom1%name
         print*, "atom info symbol ", atom1%symbol