Alkali metals are the correct answer for the group I elements.

Alkali metals are the elements present in Group I of the periodic table. This group includes lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). These elements are known for their low melting points, high reactivity, and ability to form strong bases when combined with water.

Here is a detailed explanation of why alkali metals are called group I elements:

1. Physical Properties:
- Low Melting Points: Alkali metals have low melting points, ranging from 180°C (lithium) to 28.4°C (cesium). This is due to the weak metallic bonding between their atoms.
- Soft and Silvery Appearance: Alkali metals have a soft texture and a silvery luster. They can be easily cut with a knife due to their low hardness.
- Low Density: These elements have low densities, with lithium being the least dense metal known.

2. Chemical Properties:
- High Reactivity: Alkali metals are highly reactive due to their low ionization energies. They readily lose their single valence electron to form a unipositive ion, which leads to their strong chemical reactivity.
- Reaction with Water: When alkali metals react with water, they produce hydrogen gas and strong bases. For example, sodium reacts vigorously with water, releasing hydrogen gas and forming sodium hydroxide (a strong base).
- Reaction with Oxygen: Alkali metals readily react with oxygen in the air to form oxides. This reaction is exothermic and produces a characteristic flame color, such as the yellow flame of sodium.

3. Occurrence and Uses:
- Alkali metals are relatively rare in the Earth's crust, but they can be found in various minerals and salts.
- They have several important uses, such as:
- Sodium and potassium are essential for biological processes and are found in many foods.
- Lithium is used in rechargeable batteries and medication for bipolar disorder.
- Potassium compounds are used in fertilizers.
- Sodium is widely used in the production of various chemicals, including sodium hydroxide and sodium carbonate.

In conclusion, alkali metals are called group I elements because they belong to Group I of the periodic table and exhibit characteristic physical and chemical properties, including high reactivity, low melting points, and the ability to form strong bases when combined with water.