Noble Gases: In the periodic table zero group (VIII-A) elements are known as noble gases. They are colourless, inert(unreactive), and diamagnetic gases.
Representative Elements: The elements of sub-group A are representative elements. They include metals, non-metals, and metalloids. They have further classified into two blocks;
S-BLOCK ELEMENTS: in which valence electrons occupy ns-orbital.
Or
The elements in which the last electron enters in the ns1-2 orbital.
P-BLOCK ELEMENTS: in which valence electrons occupy a p-orbital.
Or
The elements in which the last electron fills in np1-6 orbitals.
TRANSITION ELEMENTS: In the periodic table elements of sub-group ‘B’ are known as transition or heavy elements.
They are further divided into two categories:
d- BLOCK ELEMENTS (OUTER TRANSITION ELEMENTS):
The elements in which the last electron enters in ns2, (n-1) d1-10 orbital.
f – BLOCK ELEMENTS (INNER TRANSITION ELEMENTS):
The elements in which the last electron enters in ns2, (n-1) d1, (n-2) f 1-14 orbital.
| Group | Elements | Electron Configuration |
|---|---|---|
| Noble Gases | He, Ne, Ar, Kr, Xe, Rn | ns2np6 |
| Representative Elements | S-block elements: Li, Na, K, Rb, Cs, Fr P-block elements: B, C, N, O, F, Ne, Al, Si, P, S, Cl, Ar, Ga, Ge, As, Se, Br, Kr, In, Sn, Sb, Te, I, Xe, Tl, Pb, Bi, Po, At, Rn |
S-block elements: ns1-2 P-block elements: ns2np1-6 |
| Transition Elements | D-block elements: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, Cn, Nh, Fl, Mc, Lv F-block elements: 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 |
D-block elements: ns2(n-1)d1-10 F-block elements: ns2(n-1)d1(n-2)f1-14 |
The atomic radius is defined as one-half the distance between the nuclei of identical atoms that are bonded together.
OR
The total distance b/w the nucleus and the outermost orbit of the atom is called an atomic radius.
When moving across a period from Left to Right (horizontal row) of the periodic table, the atomic radius generally decreases. This is because although the number of electron shells in the atom remains the same, the effective nuclear charge increases, pulling the electrons closer to the nucleus. As the electrons are pulled closer to the nucleus, the atomic radius decreases. The increase in effective nuclear charge is due to the increase in the number of protons in the nucleus, which attracts the negatively charged electrons more strongly.
As you move down a group from top to bottom (vertical column) of the periodic table, the number of electron shells in an atom increases, causing the atomic radius to increase. This is because the added electron shell is further from the nucleus and is shielded from the attractive force of the positively charged protons by the intervening electron shells. Thus, the outermost electrons experience a weaker effective nuclear charge, and the atom as a whole is larger.
