One element has atomic weight 39. Its electronic configuration is `1s^(2), 2s^(2) 2p^(6),3s^(2) 3p^(6) 4s^(1)`. The true statement for that element is:

Options

A. Hight value of IE
B. Transition element
C. Isotone with `""_(18)Ar^(38)`
D. None

Answer

To solve the question step by step, we will analyze the given information about the element with atomic weight 39 and its electronic configuration.

### Step 1: Identify the Element
The electronic configuration provided is:
\[ 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{1} \]

To find out how many electrons this configuration represents, we can add the superscripts:
- \(1s^{2}\) contributes 2 electrons
- \(2s^{2}\) contributes 2 electrons
- \(2p^{6}\) contributes 6 electrons
- \(3s^{2}\) contributes 2 electrons
- \(3p^{6}\) contributes 6 electrons
- \(4s^{1}\) contributes 1 electron

Total number of electrons = \(2 + 2 + 6 + 2 + 6 + 1 = 19\)

### Step 2: Determine the Atomic Number
The atomic number of an element is equal to the number of electrons in a neutral atom. Therefore, this element has an atomic number of 19.

### Step 3: Identify the Element by Atomic Number
The element with atomic number 19 is Potassium (K).

### Step 4: Confirm the Atomic Weight
The atomic weight of Potassium is approximately 39, which matches the information given in the question.

### Step 5: Analyze the Electronic Configuration
The outermost electron configuration \(4s^{1}\) indicates that Potassium is an alkali metal. Alkali metals are known for having one electron in their outermost shell, which makes them highly reactive and gives them low ionization enthalpy.

### Step 6: Evaluate the Statements
Now, we need to evaluate the statements about the element:
1. **Highest value of ionization enthalpy**: This is incorrect for alkali metals since they have low ionization enthalpy.
2. **Transition element**: This is also incorrect as potassium is not a transition metal; it is an s-block element.
3. **Isotopes**: Potassium has isotopes, but the question mentions isotones. Isotones are elements with the same number of neutrons. Potassium (atomic weight 39) has 20 neutrons (39 - 19 = 20), and Argon (atomic weight 38) has 20 neutrons (38 - 18 = 20). Thus, they are isotones.

### Conclusion
The correct statement about the element is that it is isotonic with Argon.

### Final Answer
The true statement for that element is that it is isotonic with Argon.

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