Colours Of Transition Metal Cations

Copper(II) ions, denoted as Cu2+, are known to have a blue color. This is because when copper loses two electrons, it forms a positive charge of +2. This charge causes the copper ion to absorb certain wavelengths of light, particularly in the red and yellow regions of the spectrum, while reflecting or transmitting blue light. As a result, when copper(II) compounds are dissolved in water or other solvents, they appear blue in color.

Dichromate(VI) ion, Cr2O7 2-, is orange in color. This is because the compound contains chromium in its +6 oxidation state, which gives rise to the orange color. The presence of the chromate ion (CrO4 2-) and the dichromate ion (Cr2O7 2-) in solution can be identified by their distinct orange color.

The given correct answer for this question is "Green". This suggests that Nickel(II) ions (Ni 2+) are responsible for producing a green color. The green color is likely due to the absorption and reflection of specific wavelengths of light by the Nickel(II) ions. This phenomenon is known as selective absorption and is characteristic of certain transition metal ions, including Nickel(II).

The given correct answer states that Manganate(VII) is purple. Manganate(VII) refers to the compound MnO4, which is indeed purple in color. This is because the compound contains a manganese ion in its highest oxidation state (+7), which gives rise to its distinctive purple color.

Chromium(III) ions have a +3 charge, which means they have three fewer electrons than neutral chromium atoms. This charge is due to the loss of three electrons from the outermost shell of the chromium atom. When chromium(III) ions are present in a compound or solution, they absorb light in the red region of the visible spectrum and reflect or transmit light in the green region. This absorption and reflection of specific wavelengths of light give chromium(III) compounds their characteristic green color.

The given correct answer is "Pink" because when cobalt(II) ions (Co 2+) are present, they tend to form complex compounds that exhibit a pink color. This is due to the electronic transitions that occur within the cobalt ions when they absorb certain wavelengths of light. The absorbed light energy causes the cobalt ions to move from a lower energy state to a higher energy state, resulting in the observed pink color.

Chromate(VI) ion, CrO4 2-, is yellow in color. This is because the chromate ion absorbs light in the blue region of the electromagnetic spectrum and reflects or transmits light in the yellow region. The yellow color is a result of the specific arrangement of electrons in the chromate ion, which causes it to absorb certain wavelengths of light and appear yellow to our eyes.

Iron(III) ions, also known as Fe3+, have a reddish-brown color. This color is due to the presence of unpaired electrons in the d orbitals of the iron atom. When light interacts with these electrons, certain wavelengths are absorbed and others are reflected. In the case of iron(III) ions, the wavelengths of light that are reflected correspond to the reddish-brown part of the visible spectrum. Therefore, when we observe iron(III) ions, we perceive them as having a reddish-brown color.

The color of a compound is determined by the arrangement of electrons in its molecular structure. In the case of Iron(II) or Fe2+, the compound exhibits a light green color. This is because the Fe2+ ion has unpaired d-electrons in its outermost energy level. These unpaired electrons absorb light in the red region of the spectrum, resulting in the transmission of light in the green region, giving the compound its characteristic light green color.