7which physical characteristic of a solution may
indicate the presence of a transition element?
(1) its density
(2) its color
(3) its effect on litmus
(4) its effect on phenolphthalein

2= its color

Explanation:

Transition elements are present in the middle of periodic table. These are d-block elements.

These are 38 elements.

All transition elements have partially filled d orbitals.

They showed color in compound because of d-d transition.

During the d-d transition electron absorbed the energy and emit the reminder energy. The emission is usually in the form of color light.

The color of ion is complementary to the absorbed color.

The transition elements are used as a catalyst in industries such as polymer, petroleum industries.

They are ductile, conduct heat and electricity.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.