Atomic number 68

Introduction :
The element in the periodic table with atomic number 68 is Erbium.  Erbium is a element which belongs to lanthanide series in the periodic table with atomic number 68 and the symbol is Er.  Naturally Erbium is found along with other elements on earth.  It is a rare earth element which is associated with mineral gadolinite from ytterby.  It has optical fluorescent properties which is useful in laser applications like laser optical amplifier. Glasses or crystals which are doped with the element atomic number 68 (erbium) are mainly used in amplification media.

Silvery white Erbium:                                         Erbium chloride showing pink fluorescense
                                                                        under sunlight
            

Occurrence of element with atomic number 68:
In the earth crust erbium has 2.8mg/kg concentration where as in sea water it has 0.9ng/L.  This element found bound with monazite sand ores.  The sources of erbium are xenotime and euxenite.

Monazite sand:



Isotopes of element with atomic number 68:
Erbium which occurs naturally is composed of 6 stable isotopes, Er-162, Er-164, Er-166, Er-167, Er-168, and Er-170 with Er-166 being the most abundant isotope.

Properties of Element with atomic number 68:

Physical properties of Element with atomic number 68:

1. It appears as silvery white but under sun light it shows pink fluorescence.
2. Erbium has density 9.006g/cm³.
3. It decomposes at 1802K.
4. It boils at 3141K.
5. Heat of fusion is 19.90kJ/mol.
6. Heat of vaporization is 280kJ/mol.
7. Specific heat capacity at 25⁰C is 28.12J/mol/K.
8. Below 19K it is ferromagnetic, between 19-80K it is antiferromagnetic and above 80K it is paramagnetic in nature.  

Chemical Properties of Erbium with atomic number 68:
1. Erbium metal burns to form erbium (III) oxide.
    4 Er + 3 O₂ → 2 Er₂O₃
2. It reacts slowly with cold water and quickly with hot water and forms erbium oxide.
    2 Er (s) + 6 H₂O (l) → 2 Er (OH) ₃ (aq) + 3 H₂ (g)
3. Erbium reacts with all the halogens
    2 Er (s) + 3 F₂ (g) → 2 ErF₃ (s) [pink]
    2 Er (s) + 3 Cl₂ (g) → 2 ErCl₃ (s) [violet]
    2 Er (s) + 3 Br₂ (g) → 2 ErBr₃ (s) [violet]
    2 Er (s) + 3 I₂ (g) → 2 ErI₃ (s) [violet]
4. Erbium dissolves readily in dilute sulfuric acid forms yellow [Er (OH₂)₉]³⁺ hydration complexes
    2 Er (s) + 3 H₂SO₄ (aq) → 2 Er³⁺ (aq) + 3 SO2−4 (aq) + 3 H₂ (g)

 Applications of element with atomic number 68:

1. Oxide erbium which has pink color is used as a colorant for glass, porcelain and cubic zirconia. These glasses are used in sunglasses and some jewelry.
2. These are used in neutron –absorbing  control rods.
3. When erbium is doped  with optical silica glass fibers, they are used widely in optical communications.
4. These are also used to create fiber lasers.
5. These are also used in metal welding and cutting applications.
6. Erbium ions have large variety  of medical applications.