Which of the following will always have a charge of -2 when present in a compound?
Fe
O
Cr
Na
A work of caution here. The correct answer is none of those listed. I THINK
A work of caution here. The correct answer is none of those listed. I THINK the author of the problem expects the answer to be O but that is not right. It will be -2 in oxides. In peroxides it will be -1.
Fe is +2 or +3
O is -2 and -1
Cr is +2, +3, +6
Na is +1
Out of the elements listed, only O (oxygen) will always have a charge of -2 when present in a compound. Oxygen typically forms compounds by gaining two electrons, resulting in a charge of -2. In contrast, the other elements listed, namely Fe (iron), Cr (chromium), and Na (sodium), can have different charges depending on the specific compound they are part of.
To determine which element will always have a charge of -2 when present in a compound, we need to consider the element's position in the periodic table and its usual number of valence electrons.
First, let's look at the given elements:
Fe (Iron) - Iron is an element that can have different charges. It commonly forms compounds with charges of +2 or +3, but it can have other charges as well.
O (Oxygen) - Oxygen is an element that commonly forms compounds with a charge of -2.
Cr (Chromium) - Chromium is an element that can have different charges. It commonly forms compounds with charges of +2, +3, or +6, but it can have other charges as well.
Na (Sodium) - Sodium commonly forms compounds with a charge of +1.
Among the given elements, the only one that will always have a charge of -2 when present in a compound is oxygen (O). This is because oxygen is located in Group 16 (also known as Group VI) of the periodic table, and it has 6 valence electrons. Oxygen readily gains 2 electrons to achieve a stable electron configuration, which results in a charge of -2.
In contrast, the charges of iron (Fe), chromium (Cr), and sodium (Na) can vary depending on the specific compound and the oxidation state of the element.
So, the correct answer is O (oxygen).