Question

1. why is the atomic emission spectrum of each element unique?

elements have different numbers of neutrons.

the number of protons in the nucleus changes depending on the element.

each element has a unique number of protons and a unique arrangement of electrons in its energy levels.

electrons in different elements have different masses.

clear all

Explanation:

To determine why the atomic emission spectrum of each element is unique, we analyze each option:

• Option 1: Neutron number variation doesn't determine emission spectra (related to electron energy level transitions), so incorrect.
• Option 2: While protons define an element, the key for emission spectra is electron arrangements, not just proton count change description, so incorrect.
• Option 3: Atomic emission spectra result from electrons transitioning between energy levels. Each element has a unique proton number (defining the element) and unique electron arrangement in energy levels, leading to unique energy differences between levels and thus unique emission spectra. This is correct.
• Option 4: Electrons have the same mass across all elements, so this is incorrect.

Answer:

C. Each element has a unique number of protons and a unique arrangement of electrons in its energy levels.