Period 4 transition element that forms 2+ ion with a half‐filled d sub level is
Manganese (Mn)
What is the half-filled d sub-level?
Transition metals are an interesting and challenging group of elements. They have perplexing patterns of electron distribution that don’t always follow the electron-filling rules. Predicting how they will form ions is also not always obvious.
Transition metals belong to the d block, meaning that the d sublevel of electrons is in the process of being filled with up to ten electrons. Many transition metals cannot lose enough electrons to attain a noble-gas electron configuration. In addition, the majority of transition metals are capable of adopting ions with different charges. Iron, which forms either the Fe2+ or Fe3+ ions, loses electrons as shown below.
Some transition metals that have relatively few d electrons may attain a noble-gas electron configuration. Scandium is an example. Others may attain configurations with a full d sublevel, such as zinc and copper.
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<span>Total mass = 2.75g
Mass % of Mg = 1.0g x 100/2.75g = 36.36 %
Mass % of O = 1.75g x 100/2.75g = 63.64 %
Mol of Mg = 36.36/24 = 1.515
Mol of O = 63.64/16 = 3.977
Ratio of Mol of Mg and O in the substance = (1.515 : 3.977) x 2 = 3 : 8
The empirical formula of substance is Mg3O8</span>
Answer: Out of the given options 
is expected to have the highest viscosity.
Explanation:
The resistance occurred in the flow of a liquid substance is called viscosity.
More stronger is the intermolecular forces present in a substance more will be its resistance in its flow. Hence, more will be its viscosity.
For example, has strong intermolecular hydrogen bonding than the one's present in 
and 
. This is because two-OH groups are present over here.
Thus, we can conclude that out of the given options is expected to have the highest viscosity.
3NH4OH+AlCl3=Al(OH)3+3NH4Cl
