An atom has 25 protons, 30 nutrons, and 25 electrons. what is the charge of the atom's nucleus?
+25
+30
-25
-30

when number of protons and electrons are equal there is no charge on atom. Atoms is neutral.

Explanation:

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.

All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if atom has 25 protons and 25  electrons it means positive charge is equal to negative charge and atom is neutral. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.

when a neutral atom loses a electron positive charge is created because number of protons are positive charge becomes greater than negative charge.

X → X⁺ + e⁻

When a neutral atom accept  the electron negative charge is created because negative charge is become greater than positive charge.

X + e⁻ → X⁻