Choose the correct statement

Options

A. Isotopes have nearly same chemical properties
B. Isoelectronic species must be neutral
C. Na and K have nearly same `Z_("effective")`
D. All of these

Answer

To solve the question "Choose the correct statement," we will evaluate each option provided in the question.

### Step-by-Step Solution:

1. **Evaluate Option 1: Isotopes have nearly the same chemical properties.**
- Isotopes are atoms of the same element that have the same atomic number (number of protons) but different mass numbers (number of neutrons).
- Since isotopes have the same number of electrons, they exhibit similar chemical behavior.
- Therefore, this statement is **correct**.

2. **Evaluate Option 2: Isoelectronic species must be neutral.**
- Isoelectronic species are atoms or ions that have the same number of electrons.
- These species can be either neutral or charged. For example, CN⁻ (which has 14 electrons) and CO (which is neutral and also has 14 electrons) are both isoelectronic but one is charged and the other is neutral.
- Thus, this statement is **incorrect**.

3. **Evaluate Option 3: Sodium and potassium have nearly the same Z effective.**
- The effective nuclear charge (Z effective) is influenced by the number of inner electrons and the distance of the outermost electrons from the nucleus.
- Sodium (Na) has the electronic configuration of 2, 8, 1, while potassium (K) has the configuration of 2, 8, 8, 1.
- The number of inner electrons is different for sodium and potassium, leading to different Z effective values.
- Hence, this statement is **incorrect**.

4. **Evaluate Option 4: All of this.**
- Since options 2 and 3 are incorrect, this option cannot be correct.
- Therefore, this statement is **incorrect**.

### Conclusion:
After evaluating all the options, the correct statement is **Option 1: Isotopes have nearly the same chemical properties**.

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