Question

Which of the following is a lyophobic colloid?
A.Sulphur sol
B. Starch
C. Gum arabica
D. Gelatin

Answer 1

Ionisation energy is a periodic trend that varies across the periodic table .

Complete answer:
Ionisation energy is defined as the minimum amount of energy that is needed in order to remove the most loosely bound electron from its valence shell.
(a) First period : It correspond to the filling of electrons in the first energy shell i.e., (K shell), n = 1, since this energy shell has only one orbital, i.e., 1s which can accommodate only two electrons, therefore the first period contains only two elements. Hydrogen and Helium
Second period : It corresponds to the filling of electrons in the 2nd energy shell (L shell) i.e. n = 2. It starts with Li (Z = 3) which has three electrons where two electrons are in the 1s orbital and the third electron enters the 2s orbital. The next element Be(Z = 4) has four electrons. From next element B (Z =5) the 2p orbitals are filled with electrons and the L shell completes at Ne (Z = 10) .
Third period : This period corresponds to the filling of electrons in the third shell i.e., n = 3. This shell has nine orbitals (one 3s, three 3p and five 3d). However according to the energy level diagram of multielectron atoms, 3d-orbitals have high energy so filled after 4s-orbital. Consequently the third period contains only four orbitals (3s and 3p) accommodating only eight electrons. Thus it has only eight elements. It begins at sodium (Z = 11) where the added electron enters the 3s orbital. Successive filling of electrons completing the 3s and 3p orbitals ends at Argon (Z = 18).
Fourth period : It corresponds to the filling of electrons in the fourth energy level i.e., n = 4. It starts with potassium (Z = 19) and the added electron goes to 4s-orbital which completes at calcium (Z = 20). After filling 4s orbital filling of five 3d-orbital starts that can accommodate ten electrons. Before the 4p-orbital is filled 3d orbitals are filled first being energetically more favourable and we come across the so called 3d transition series of elements. This series starts at scandium (Z = 21). The 3d orbitals get completely filled at zinc (Z = 30) . orbitals start at gallium (Z = 31) and end at krypton (Z = 36).
Fifth period : Fifth period corresponds to the fifth shell i.e., n = 5. Like the fourth period it also has nine orbitals (one 5s, three 5p and five 4d) which can accommodate eighteen electrons i.e., it can have eighteen elements. The fifth period starts at rubidium (Z = 37) where one electron enters the 5s-orbital After 5s-orbital filling, the filling of 4d-orbital begins which starts at yttrium (Z = 39) and ends at cadmium (Z = 48). These ten elements are known as 4d-transition series. Therefore the filling of 5p-orbital starts from indium (Z = 49) and ends at xenon (Z = 54).
Sixth period : It corresponds to the filling of the sixth energy level i.e., n = 6. Since in this period only sixteen orbitals (one 6s, seven 4f, five 5d and three 6p) are available, thereby the sixth period contains thirty two elements. It begins with caesium (z = 55) in which the electron enters the 6s-orbital and ends at radon (z = 86) in which the filling of 6p-orbitals is complete. These fourteen elements constitute the first (or 4f) inner transition series called lanthanide series or lanthanoids. These are placed separately from the main frame of the periodic table at the bottom of the periodic table.
Seventh period : It corresponds to the filling of the seventh energy shell, i.e., n = 7. Like the sixth period, it also contains thirty two elements due to the sixteen orbitals (one 7s, seven 5f, five 6d and three 7p). This includes most of the man made radioactive elements. The filling of orbitals starts with 7s where The first electron enters into 7s of Fr(Z = 87). The seventh period ends at an element with atomic number of element 118 which will belong to the noble gas family.
So Sulphur has the lowest ionisation energy as it has a larger atomic size than others.

Note:
Ionisation energy decreases down the group as atomic size increases down the group and increases along the period as atomic size decreases.