Period: 3rd (m-shell)

The third period (m-shell) follows the pattern of the l-shell; it holds another eight electrons in the 3s and 3p orbitals. Elements of the 3rd period are sodium (11 electrons) to argon (18 electrons).

11Na

Sodiumsilvery white metallic

12Mg

Magnesiumshiny grey solid

13Al

Aluminumsilvery gray metallic

14Si

Siliconcrystalline, reflective with bluish-tinged faces

15P

Phosphoruswhite, red and violet are waxy, black is metallic-looking

16S

Sulfuryellow sintered microcrystals

17Cl

Chlorinepale yellow-green gas

18Ar

Argoncolorless gas exhibiting a lilac/violet glow when placed in an electric field

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 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og

Legend

1st (k-shell)2nd (l-shell)3rd (m-shell)4th (n-shell)5th (o-shell)6th (p-shell)7th (q-shell)