Group 1A elements are also called:
A noble gases.
B halogens.
C alkaline earth metals.
D alkali metals.
E transitions metals
The Correct Answer and Explanation is :
The correct answer is D) alkali metals.
Group 1A elements are also called alkali metals. This group includes the elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). These elements are characterized by their highly reactive nature, especially with water, and their tendency to form strong bases (alkalies) when combined with water, which is how they got their name.
Characteristics of Alkali Metals:
- Highly Reactive: Alkali metals are known for their high reactivity, particularly with water. When they react with water, they produce hydrogen gas and a hydroxide of the metal, often generating enough heat to ignite the hydrogen gas. This reactivity increases as you move down the group. For example, potassium reacts more vigorously than sodium.
- Softness: These metals are typically soft and can be easily cut with a knife. Lithium is the hardest of the alkali metals, while cesium is the softest.
- Low Melting and Boiling Points: Alkali metals have low melting and boiling points compared to most other metals. These points decrease as you move down the group.
- Good Conductors of Electricity: Alkali metals are excellent conductors of electricity due to their free-flowing outer electrons.
- Formation of +1 Ions: Alkali metals have one electron in their outermost shell, which they readily lose to form a +1 ion. This is why alkali metals tend to form salts when they react with halogens.
Why Not the Other Choices:
- A) Noble gases: These are found in Group 18 and are characterized by their lack of reactivity, owing to their full valence electron shells.
- B) Halogens: These are found in Group 17 and are highly reactive nonmetals, but they are not alkali metals.
- C) Alkaline earth metals: These are found in Group 2 and are also metals, but they have two electrons in their outer shell and are less reactive than alkali metals.
- E) Transition metals: These are found in the d-block of the periodic table and have varying properties, including being harder and less reactive than alkali metals.
Thus, the Group 1A elements are best known as alkali metals due to their distinctive chemical properties and reactivity.