What is the relative abundance of sodium by weight in the earth's crust?

Explanation

To determine the relative abundance of sodium by weight in the Earth's crust, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Elements in the Earth's Crust**: We need to consider the most abundant elements found in the Earth's crust. The most common elements include oxygen, silicon, aluminum, iron, calcium, sodium, magnesium, potassium, and titanium.

2. **List the Abundance of Each Element**: The relative abundance of these elements by weight percentage is as follows:
- Oxygen: 46%
- Silicon: 28%
- Aluminum: 8.3%
- Iron: 5.6%
- Calcium: 4.2%
- Sodium: 2.5%
- Magnesium: 2.4%
- Potassium: 2.0%
- Titanium: 0.61%

3. **Locate Sodium's Position**: From the list, we can see that sodium has a weight percentage of 2.5%.

4. **Determine the Relative Abundance**: Sodium is the sixth most abundant element in the Earth's crust based on its weight percentage.

5. **Conclude the Answer**: Therefore, the relative abundance of sodium by weight in the Earth's crust is 2.5%, and it ranks as the sixth most abundant element.

### Final Answer:
The relative abundance of sodium by weight in the Earth's crust is **2.5%**, and it is the **sixth** most abundant element.

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