0.6 Chapter 2. solid state of matter.  (Page 7/7)

For n=6, l can be 0 , 1, 2 , 3 , 4 and 5. This marks the Sixth Period.

Here we have K Shell , L-Shell , M-Shell are filled up and N-Shell and O-Shell is partially filled up. K,L, M full and N(partially) and O(partially) corresponds to Xe. Partially filled N-Shell and partially filled O-Shell is in the process of getting filled along with empty P-Shell up as shown in Table 2.11.

Table 2.11. Elements of SIXTH Period.

†La,Hf,Ta,W,Re,Os,Ir,Pt,Au,Hg are the d-Block Transition elements which are there due to belated filling up of d-orbitals in O-Shell which has 10 electron states permissible from 5d ¹ to 5d ¹⁰ .

Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu are f-Block Transition elements which are due to belated filling up of N-Shell f-orbital belated fillings from 4f ¹ to 4f ¹⁴ .

Section 2.3.1.Applications of Noble Gases

Argon is used in glass chambers to provide inert atmosphere as for instance in Incandescent Lamp and in Siemen’s Reactor. Helium is used as breather gas. He-O ₂ is used as breathing gas for deep-sea divers at a depth of 55m. This prevents oxygen toxemia. This also prevents Nitrogen narcosis. Helium gases have replaced highly inflammable Hydrogen gases in lighter than air applications.

Noble gases have multiple stable isotopes except Radon which is radio-active. Radon has a half-lifetime of 3.8days. It decays to Helium and Polonium which further decays to lead.

In each PERIOD of the periodic table, Noble gas has the highest first Ionization Energy and the Group I alkali metal has the lowest Ionization energy. There is only weak Vander Waal’s force acting between Noble gas atoms. Hence they have very low Melting Point and Boiling Point.

Noble Gases are nearly Ideal Gases and their deviations from Ideal Gas Law give important clues regarding the inter-atomic distances of the gas atoms.

If an atom has only a under-populated sub-shell, it will tend to lose them to become positively ionized as it happens in alkali metal. When metal atoms bond, a metallic bond occurs. When an atom has a nearly full electron sub-shell, it will try to find electrons from another atom so that it can fill its outer sub-shell and become electro-negative. These elements are usually described as nonmetals. The bond between two nonmetal atoms is usually a covalent bond. Whereas metal and nonmetal atom come together and an ionic bond occurs. There are also other, less common, types of bond but the details are beyond the scope of this material. On the next few pages, the Metallic, Covalent and Ionic bonds will be covered in detail.