Problem 134 - A Complete Resource Book in Chemistry for JEE Main

Question

An element with atomic number 34 belongs to which period?

Step-by-Step Solution

Answer

The element with atomic number 34 is in the 4th period.

Step 1: Understanding Atomic Number

The atomic number of an element is the number of protons in the nucleus of an atom of that element. We are given an atomic number of 34.

Step 2: Using the Periodic Table

In the periodic table, elements are arranged in order of increasing atomic number. To determine the period of an element, locate the element with atomic number 34.

Step 3: Locate Atomic Number 34

By examining a periodic table, identify the element selenium (Se) which has an atomic number of 34.

Step 4: Determine the Period

On the periodic table, periods are the horizontal rows. Selenium is located in the fourth period.

Key Concepts

Atomic Number

The atomic number of an element is a fundamental property that defines the identity of the element. It represents the number of protons found in the nucleus of an atom. This number is unique for each element and is used to arrange the elements on the periodic table.

• Atomic number aids in distinguishing one element from another.
• For example, if an element has an atomic number of 34, it means there are 34 protons in the nucleus of its atom.
• The atomic number is a key factor in determining the element's position on the periodic table.

Understanding the atomic number helps predict the chemical properties and behaviors of the element. The periodic table is arranged in order of increasing atomic numbers from left to right, starting with hydrogen, which has an atomic number of 1.

Selenium

Selenium is an interesting element with the atomic number 34, which means it has 34 protons. It is represented by the symbol 'Se' on the periodic table and is known for its non-metallic properties.

• Selenium is commonly found in the Earth's crust and is acquired through various biological processes.
• It is essential for the functioning of certain enzymes within the human body.
• Selenium can exhibit different chemical behaviors, as it exists in multiple oxidation states.

Often, selenium is used in glassmaking and electronics, as well as in some dietary supplements due to its health benefits. The discovery of selenium dates back to 1817, highlighting its long-standing significance in both elemental and applied sciences.

Periods in Periodic Table

In the periodic table, periods refer to the horizontal rows. Understanding periods is crucial, as they provide insights into the electron configuration and reactivity of the elements they comprise.

• There are seven periods in the periodic table, each corresponding to the outer electron shell of the elements in that row.
• Elements within the same period have the same number of atomic orbitals but differ in their reactivity and characteristics.
• For example, selenium is located in the fourth period, indicating it has four electron shells.

The periodic trends observed across periods, such as changes in atomic size and electronegativity, are vital in predicting the behavior of elements in chemical reactions. Hence, periods play a pivotal role in the organization and utility of the periodic table for scientific studies and practical applications.