Problem 45 - A Complete Resource Book in Chemistry for JEE Main

Question

In India at the occasion of marriages, the fire works are used, which of the following gives green flame? (a) \(\mathrm{K}\) (b) \(\mathrm{Ba}\) (c) \(\mathrm{Be}\) (d) \(\mathrm{Na}\)

Step-by-Step Solution

Answer

Barium (\(\mathrm{Ba}\)) gives a green flame.

Step 1: Understanding Flame Colors

Different elements produce different colors when burned, a property used in fireworks. This phenomenon is due to specific electrons in the element being excited to higher energy levels and releasing specific wavelengths of light (color) when they return to lower energy levels.

Step 2: Identify Elements and Their Flame Colors

Let's recall the typical flame colors for the given elements: - Potassium ( \( \mathrm{K} \)) typically produces a lilac or light purple flame.- Barium ( \( \mathrm{Ba} \)) produces a green flame.- Beryllium ( \( \mathrm{Be} \)) does not have a characteristic flame color due to the high energy of its emissions.- Sodium ( \( \mathrm{Na} \)) is known for its bright yellow flame.

Step 3: Select the Correct Option

Based on the typical flame colors, the element that gives a green flame is Barium ( \( \mathrm{Ba} \)).

Key Concepts

Flame Colors

Flame colors are a fascinating part of chemistry that can be witnessed during fireworks, in laboratories, and various other events involving burning substances. When a chemical element is heated, it emits light of specific wavelengths, which appear as distinct colors to our eyes. This is why fireworks showcase such a vibrant array of hues.

The color emitted by a flame is determined by the element's specific electrons becoming energized. Different elements produce different flame colors because each element has unique energy levels for its electrons. When these electrons are excited to higher energy states and then drop back down, they emit light specific to the difference in those energy levels. This light falls into the visible spectrum, presenting to us as vivid colors.

Some examples of common flame colors include:

• Potassium (4K4) - Lilac or light purple
• Barium (4Ba4) - Green
• Sodium (4Na4) - Bright yellow

These colors are useful for identifying chemical compounds and are used in various fields, from forensic science to entertainment.

Electron Excitation

Electron excitation is a fundamental concept that explains the colorful displays we see when burning certain elements. When an atom absorbs energy—often in the form of heat or electrical energy—its electrons can move from a lower energy level to a higher one. This process is called excitation.

Once the external energy source, such as a flame, provides enough energy, the electron gets a 'boost' into a more energetic state. However, electrons can't stay in this high energy state forever. As they return back to their original, lower energy level, they release the absorbed energy as light. The color of this light depends on the energy difference between the two electron states.

This process is fundamental to understanding phenomena like flame tests or the operation of neon lights. It's also a bedrock concept in studying atomic structure and quantum mechanics.

Chemical Elements

Chemical elements are the building blocks of matter and each has its characteristics and unique properties. They are distinguished not just by their atomic number and mass but also by how they behave when introduced to energy sources, like heat.
During a flame test, these properties come to light. Each element responds differently due to its unique electron configuration. Here's how some common elements behave when subjected to a flame test:

• Potassium (K): When it burns, it gives off a lilac flame due to its specific electron transitions.
• Barium (Ba): It is well known for producing a brilliant green flame when excited.
• Sodium (Na): It emits a bright yellow flame that is very intense and easily recognizable.

Experiments with chemical elements, such as flame tests, provide insights into electron arrangements and transitions. These tests help in identifying unknown substances and are widely used in chemistry labs around the world.