Ionization energy is always positive for an element and successive ionization energies always gradually increase.
The successive ionization energy for an element is given below in mJ/mole.
0.7865, 1.5771,3.2316, 4.3555, 16.091, 19.785, 23.786, 29252
Predict the number of valence shell electrons in the given element. 

Options

A. 1
B. 2
C. 3
D. 4

Answer

To determine the number of valence shell electrons in the given element based on the provided successive ionization energies, we can follow these steps:

### Step 1: Analyze the Ionization Energies
The given successive ionization energies are:
- 1st: 0.7865 mJ/mole
- 2nd: 1.5771 mJ/mole
- 3rd: 3.2316 mJ/mole
- 4th: 4.3555 mJ/mole
- 5th: 16.091 mJ/mole
- 6th: 19.785 mJ/mole
- 7th: 23.786 mJ/mole
- 8th: 29252 mJ/mole

### Step 2: Identify the Significant Jump
Observe the values for the ionization energies:
- The first four ionization energies (1st to 4th) show a gradual increase.
- However, there is a significant jump between the 4th (4.3555 mJ/mole) and the 5th (16.091 mJ/mole) ionization energy.

### Step 3: Interpret the Jump
The large increase in ionization energy from the 4th to the 5th indicates that after removing four electrons, the next electron (the fifth one) is being removed from a much more stable electronic configuration (likely a noble gas configuration). This suggests that the element has four valence electrons.

### Step 4: Conclude the Number of Valence Electrons
Since the jump occurs after the removal of the fourth electron, we can conclude that the element has **4 valence electrons**.

### Final Answer
The number of valence shell electrons in the given element is **4**.

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