17  Chlorine

 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      

+--------------------+
| 17     ____ _      |
|       / ___| |     |
|      | |   | |     |
|      | |___| |     |
|       \____|_|     |
|                    |
|      Chlorine      |
|       35.45 u      |
+--------------------+

Electron Configuration: [Ne]3s2 3p5
Electronegativity:      3.16
Atomic Radius:          175 pm
Ionization Energy:      12.968 eV
Electron Affinity:      3.617 eV
Oxidation States:       +7, +5, +1, -1
Standard State:         Gas
Melting Point:          171.65 K
Boiling Point:          239.11 K
Density:                0.003214 g/cm3
Family:                 Halogen
Year Discovered:        1774
Number of Neutrons:     18
Number of Protons:      17
Number of Electrons:    17
Number of Valence:      7
Valency:                1
Group:                  17
Period:                 3
Shell:                  p-shell
Specific Heat:          0.479 J/g K
Radioactive:            0
Occurrence:             Natural
Source:                 Dying high-mass stars