34  Selenium

 H                                                  He
 Li Be                               B  C  N  O  F  Ne
 Na Mg                               Al Si P  S  Cl Ar
 K  Ca Sc Ti V  Cr Mn Fe Co Ni Cu Zn Ga Ge As[Se]Br Kr
 Rb Sr Y  Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I  Xe
 Cs Ba La Hf Ta W  Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
                                                      
       Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu      
       Th Pa U  Np Pu Am Cm Bk Cf Es Fm Md No Lr      

+--------------------+
| 34  ____           |
|    / ___|  ___     |
|    \___ \ / _ \    |
|     ___) |  __/    |
|    |____/ \___|    |
|                    |
|      Selenium      |
|       78.97 u      |
+--------------------+

Electron Configuration: [Ar]4s2 3d10 4p4
Electronegativity:      2.55
Atomic Radius:          190 pm
Ionization Energy:      9.752 eV
Electron Affinity:      2.021 eV
Oxidation States:       +6, +4, -2
Standard State:         Solid
Melting Point:          493.65 K
Boiling Point:          958 K
Density:                4.809 g/cm3
Family:                 Nonmetal
Year Discovered:        1817
Number of Neutrons:     45
Number of Protons:      34
Number of Electrons:    34
Number of Valence:      6
Valency:                2
Group:                  16
Period:                 4
Shell:                  p-shell
Specific Heat:          0.321 J/g K
Radioactive:            0
Occurrence:             Natural
Source:                 Dying high-mass stars