Why are sodium (Na) and potassium (K) in the same group on the periodic table?
• They are both colorless.
• They have similar reactivity.
• They are both hard and brittle.
• They have similar atomic weights.
Sodium (Na) and potassium (K) are in the same group on the periodic table because they have similar chemical properties and reactivity.
To determine this, we can look at the periodic table. The modern periodic table is arranged based on the atomic number of elements. Elements in the same vertical column or group share similar chemical properties. Sodium and potassium are both located in Group 1, also known as the alkali metals.
Now, let's look at the given options to see why sodium and potassium are in the same group:
1. They are both colorless: This statement is not true. Sodium and potassium have different iconic colors. Sodium has a yellowish hue, while potassium has a grayish appearance.
2. They have similar reactivity: This statement is true. Sodium and potassium are both highly reactive metals. They react vigorously with water and oxygen, forming hydroxides and oxides respectively.
3. They are both hard and brittle: This statement is not true. Sodium and potassium are soft and can be easily cut with a knife. They have low hardness and malleability.
4. They have similar atomic weights: This statement is partially true. While sodium and potassium have similar atomic weights (22.99 u and 39.10 u respectively), the arrangement on the periodic table is primarily based on their chemical properties, not just their atomic weights.
Therefore, the correct reason why sodium and potassium are in the same group on the periodic table is because they have similar reactivity.