Arrange in decreasing order as directed.
(a) Decreasing order of `EN: C, O, N,F`

Explanation

[`EN` increase along the period, `:. EN` of `F gt O`]
Aluminium `(Al)` belongs to `3rd` period. [ `EN` decreases down the group `(darr)`]

Althogh size of an atom decreases along the period `(darr)` but in a period, size of nolbe gas in highest. `Ar` belongs to `3 rd` period whereas `Br` belongs to `4 th` period.
`:.` Size of `Br gt` Size of `Ar`
Similarly, although both `Ca^(2+)` and `Mg^(2+)` ions have same charge, but `Ca` belongs to `4 th` period and `Mg` belongs to `3rd` period.
`:.` Size of `Ca^(2+) gt` size of `Mg^(2+)`
c. `EA:Cl gt F gt O gt C gt N gt Be`
Among halogens decreasing order of `EA` or `Delta_(Ag)H^(ɵ)=Cl gt F gt I`
Generally `EA` increase along the period `(rarr)`
Therefore, order of `EA` should be `O gt N gt C`
But there is exception in the `EA` of `N` and `C`, Since `N` has half-filled stable configuration, so it is difficult to add electron to `N` as compared to `C`.
`:. EA` of `C gt N`
Among `Be, C,N,O` and `F` (all of them belong to `2 nd` period) `EA` of `Be` is the least. Hence the order is as given above.
d. ` IE gt Cl gt Br gt I [{:("Generally" IE"decreases"),("down the group""("darr")"):}]`
`EA:Cl gtF gt Br gtI [{:("Exception in case"),("of" Cl gt F):}]`
e. EN:

Generally `EN` increases along the same period `(rarr)`.
Therefore , `EN` of `2 nd` period `gt EN` of `3 rd` period. But `EN` of `N` ( 2nd period) is the least, and is an exception due to half-filled stable configuration.

`IE` increases along the same period `(rarr)` and `IE` of noble gas `(Ne)` is the highest.
`IE` of alkali metal `(Na)` is less as compared to `Na^(o+)` ion, since it is very difficult to remove an electron from a positve ion.
Generally, `IE` decreases down the group `(darr)`. so `IE` of `O gt Na`.
Hence the order is as given above.
g. Electropositive character: `Na gt Zn gt Cu`
Group `1` is more metallic ( or electropositive character) than group `2`. So, `Na` is most metallic than `Zn` and `Cu`. Similarly, `d`-block elements have more electropositive character than `p`-block elements.
Hence the electropositve character is as given below.
Note: In the metallic character series, the electropositve character (or reducing character is in the order)
`Na gt Mg gtZn gtFe gtNi gt Cu gt Ag`
Note that in metallic character series, PSBC MAZINTL CHAAP. `Zn` comes after `s`-block elements.