Caesium (Cs) has the greatest electropositive nature among all the given elements because as we move across a period, electropositive character decreases whereas down a group, it decreases.

Atomic size increases down a group due to increase in distance between the outermost electrons and nucleus.

The correct order of arrangement of elements in a period according to their metallic character is Li < Na < K < Rb < Cs. As we go down a group, metallic character increases.

Electronegativity refers to the tendency of an atom to attract bonding electrons.

With respect to chlorine, hydrogen will be electropositive.

Germanium is a metalloid.

The correct decreasing order of arrangement of atomic radii of F, F^–, O and O^2– is O^2– > F^– > O > F because size of the anions is greater than the corresponding atoms and also across a period, the size of atom decreases.

Silicon belongs to carbon family. Thus, it has 4 electrons in its valence shell.

From the given oxides, Na₂O forms the strongest base.

The principal quantum number ‘n’ represents the size of the orbital.

The element which accepts electrons rarely to form anion belongs to VIII A group and 3^rd period.

Electron affinity is defined as the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion. Halogens have the greatest electron affinity as by gaining one electron, they attain noble gas configuration. Thus, from the given elements, fluorine has the maximum electron affinity.

Helium has the lowest electronegativity because it is a noble gas and noble gases are chemically very stable as they have the maximum number of valence electrons that their outer shell can hold. Thus, the noble gas atom, being electrically neutral, would not be able to exert much attractive force on free-ranging electrons, i.e. low electronegativity.

Non-metals can have the tendency to form anions. Thus, from given options, (N, O and F) are non-metals and thus, can form anion easily.

Gallium is more electronegative than aluminium due to increase in effective nuclear charge.

The rare gas which is present most abundantly in air is argon.

The electronic configuration of chromium (Z = 24) is 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵, 4s¹.

Electronegativity decreases as you go down a group within the periodic table. This is because of the longer distance between the nucleus and the outer valence electron shell within an atom. This decreases the attraction. Thus, the correct order of electronegativities is O > N > P.

The increasing order of atomic radii among the given halogens is F, Cl, Br, I because as we move down a group, the size of atom increases.

Na²⁺ is of the smallest size.