Question

In the periodic table, how many elements are found in each of the following? a. the halogen family b. the alkali family c. the lanthanide series

Short answer

a. The halogen family has 5 elements. b. The alkali family has 6 elements. c. The lanthanide series has 15 elements.

Step-by-step solution

Identify the halogen family in the periodic table

The halogen family consists of elements of Group 17 in the periodic table. They are characterized by having seven valence electrons. In this group, there are five elements, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

Count the elements in the halogen family

We can count the number of elements in the halogen family, which is 5 elements. The answer for (a) is 5 elements.

Identify the alkali family in the periodic table

The alkali family consists of elements in Group 1 of the periodic table, excluding hydrogen. They possess one valence electron and are highly reactive. The alkali family has six elements, including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

Count the elements in the alkali family

We can count the number of elements in the alkali family, which is 6 elements. The answer for (b) is 6 elements.

Identify the lanthanide series in the periodic table

The lanthanide series consists of 15 elements located in the f-block of the periodic table (elements with atomic numbers 57-71). They are also called rare earth elements and include elements like lanthanum (La), cerium (Ce), and neodymium (Nd), among others.

Count the elements in the lanthanide series

We can count the number of elements in the lanthanide series, which is 15 elements. The answer for (c) is 15 elements. Final Answers: a. The halogen family has 5 elements. b. The alkali family has 6 elements. c. The lanthanide series has 15 elements.

Key concepts

Halogen Family

The halogen family is an interesting group of elements located in Group 17 of the periodic table. They are best known for their seven valence electrons, which make them highly reactive, particularly with elements from the alkali family. Valence electrons are the outermost electrons of an atom and are crucial in bonding with other atoms.

Halogens are also known for their ability to form salts when they react with metals. A common example is sodium chloride ( NaCl ), better known as table salt. This group includes five elements:

• Fluorine (F)
• Chlorine (Cl)
• Bromine (Br)
• Iodine (I)
• Astatine (At)

Each has distinct properties and uses. For instance, chlorine is often used for disinfecting water, while fluorine is key in dental health. Understanding the halogens is vital in chemistry due to their crucial role in forming compounds.

Alkali Family

The alkali family occupies Group 1 of the periodic table and consists of six elements. These elements are highly reactive, which is related to their possession of a single valence electron. Since the alkali metals eagerly lose this solitary electron, they readily participate in chemical reactions.

Alkali metals are typically soft and have low melting points. They are so reactive they are usually stored in oil to prevent them from reacting with moisture in the air. This group includes:

• Lithium (Li)
• Sodium (Na)
• Potassium (K)
• Rubidium (Rb)
• Cesium (Cs)
• Francium (Fr)

Though francium is very rare and radioactive, the others have significant uses. For example, sodium and potassium are essential elements in biological systems, while lithium is widely used in batteries. Understanding the alkali family is crucial for learning about element reactivity and their applications in everyday life.

Lanthanide Series

The lanthanide series, often referred to as the "rare earth elements," includes a fascinating group of 15 elements in the f-block, ranging from atomic numbers 57 to 71. They are positioned within two rows at the bottom of the periodic table. Despite their "rare" name, some lanthanides are relatively abundant in the earth's crust.

These elements typically exhibit strong magnetic properties and are known for their optical applications. The series includes elements like:

• Lanthanum (La)
• Cerium (Ce)
• Neodymium (Nd)

Each of these elements has unique properties used in various high-tech applications. For instance, neodymium is a key component in powerful magnets used in electronics and technology. The lanthanide series is essential in modern technological applications, making them an important study area within chemistry.