The correct order of increasing radii of the elements`Si,Al,Na and P` is

Options

A. `Si lt Al lt P lt Na`
B. `P lt Si lt Al lt Na`
C. `Al lt Si lt P lt Na`
D. `Al lt P lt Si lt Na`

Answer

To determine the correct order of increasing atomic radii for the elements silicon (Si), aluminum (Al), sodium (Na), and phosphorus (P), we need to analyze their positions in the periodic table and apply the trends in atomic radii.

### Step-by-Step Solution:

1. **Identify the Group and Period of Each Element**:
- Sodium (Na): Group 1, Period 3
- Aluminum (Al): Group 13, Period 3
- Silicon (Si): Group 14, Period 3
- Phosphorus (P): Group 15, Period 3

2. **Understand the Trend in Atomic Radii**:
- Atomic radii increase as you move down a group due to the addition of electron shells.
- Atomic radii decrease as you move from left to right across a period due to the increasing nuclear charge, which pulls the electrons closer to the nucleus.

3. **Compare the Elements**:
- All four elements are in the same period (Period 3), so we will compare them based on their group positions.
- In Period 3, the order of atomic radii from largest to smallest is generally: Na > Al > Si > P.
- Sodium (Na) has the largest atomic radius because it is the furthest left in the period.
- Aluminum (Al) is next, followed by Silicon (Si), and finally Phosphorus (P), which has the smallest atomic radius.

4. **Establish the Order of Increasing Atomic Radii**:
- Based on the comparisons, we can conclude the order of increasing atomic radii is:
- P < Si < Al < Na

### Final Answer:
The correct order of increasing radii of the elements Si, Al, Na, and P is:
**P < Si < Al < Na**