Isotopes are atoms of the same element that have different numbers of neutrons.

Let’s check each statement.

I. Atomic number

The atomic number is the number of protons in the nucleus.

Since isotopes are atoms of the same element, they must have the same number of protons.

So isotopes have the same atomic number.

Statement I is correct.

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II. Electronic configuration

For neutral atoms:

$$\text{number of electrons} = \text{number of protons}$$

Since isotopes have the same number of protons, neutral isotopes also have the same number of electrons.

Electronic configuration depends on the number and arrangement of electrons, so isotopes have the same electronic configuration.

Statement II is correct.

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III. Chemical properties

Chemical properties mainly depend on the arrangement of electrons, especially the outer-shell electrons.

Since isotopes have the same electronic configuration, they generally have the same chemical properties.

Statement III is correct.

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IV. Mass number

The mass number is:

$$\text{mass number} = \text{number of protons} + \text{number of neutrons}$$

Isotopes have the same number of protons but different numbers of neutrons.

Therefore, their mass numbers are different.

Statement IV is incorrect.

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So the correct statements are:

$$\text{I, II and III}$$

Therefore, the correct answer is:

D) I, II and III