Question

Question #1b7a2

Answer 1

(a) The given formula is AlCl . It is incorrect. The correct formula can be written if we know the valencies of different elements. The valency of Aluminum is +3 as it loses three electrons to achieve stable noble gas configuration like Neon.
Each Chlorine atom has valency of -1 as it gains one electron to achieve stable noble gas configuration like Argon.

`Al^(3+)` , `Cl^(1-)` To balance the positive and negative charges
for one Aluminum atom ,three chlorine atoms can unite as to make +3 charge equal to -3 charge.
So the formula will be `Al_1Cl_3`

`Na_3`S`O_`4 (incorrect). The valency of Sodium is +1 as it loses one electron to achieve stable noble gas configuration like Neon.
S`O_4` has valency of -2.
`Na^(1+)` S`O_4^(2-)` To balance the positive and negative charges for one sulfate ion ,two Sodium atoms can unite as to make -2 charge equal to +2 charge.
So the formula will be `Na_2SO_4`

BaOH2 ( incorrect). The valency of Barium is +2 as it loses two electrons to achieve stable noble gas configuration.
Each Hydroxide Ion `OH^ (-1)` has charge of -1 unit.
To balance the positive and negative charges
for one barium ion ,two hydroxide ions can unite as to make +2 charge equal to -2 charge.
`Ba^(2+)` and `OH^(-1)` , So the formula will be `Ba_1OH_2`

`Fe^(2+)` , `O^(2-)` To balance the positive and negative charges for one oxide ion, one Iron atom can unite as to make -2 charge equal to +2 charge.
The formula is `Fe_2O_2` and simplifying it the formula will be
FeO