Group 1 metals are called alkaline metals because their oxides and hydroxides form alkaline solutions when dissolved in water.

Here's a breakdown:

* Alkaline refers to a substance that has a pH greater than 7. This means it is basic and has a bitter taste.

* Oxides are compounds formed when a metal reacts with oxygen.

* Hydroxides are compounds formed when a metal reacts with water and releases hydrogen gas.

When Group 1 metals react with water, they form hydroxides which are highly soluble in water. These hydroxides, like sodium hydroxide (NaOH) and potassium hydroxide (KOH), dissociate in water to release hydroxide ions (OH⁻), which increase the pH of the solution, making it alkaline.

For example, sodium reacts with water to form sodium hydroxide:

```

2Na + 2H₂O → 2NaOH + H₂

```

The sodium hydroxide then dissolves in water to form a highly alkaline solution.

Therefore, the term "alkaline metals" reflects their ability to form alkaline solutions due to the basic nature of their oxides and hydroxides.