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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<u>Answer:</u>
<u>For a:</u> Yes, he has gained weight.
<u>For b:</u> The number of onions required is 1.
<u>Explanation:</u>
We are given:
Weight of Brandon checked earlier = 183 lb
Converting this into kilograms, we use the conversion factor:
1 kg = 2.205 lb
So, 
And, weight of Brandon measured at the health club = 85.0 kg
As, the weight at the health club is more than the previous measured weight. So, Brandon has gained weight.
We are given:
Amount of diced onions a recipe calls = 125 g
Mass of 1 onion = 4 oz
Converting the mass of 1 onion to ounces, we use the conversion factor:
1 oz = 28.35 g
So, 
To calculate the number of onions, we use the equation:
Hence, the number of onions required is 1.
As density increases, the amount of salt or salinity increases. Salinity can decrease from the melting of ice or increase from the freezing of ice<span />
