Atomic Structure — Set 2
Chemistry · परमाणु संरचना · Questions 11–20 of 50
Which subatomic particle is the lightest in weight?
Correct Answer: B. Electron
The mass of an electron is approximately 1/1836th of the mass of a proton. Because they are so light, their mass is usually ignored when calculating the atomic mass. They move at very high speeds within the electron shells.
The atomic number of an element is always equal to the number of?
Correct Answer: D. Protons
The number of protons in the nucleus defines the identity of an element. This value is known as the atomic number and is denoted by the letter Z. In a neutral atom, this number also equals the total number of electrons.
According to Bohr's model, what happens when an electron jumps from a lower energy level to a higher one?
Correct Answer: B. Energy is absorbed
Electrons require extra energy to move to a shell further from the nucleus. This energy is typically absorbed in the form of electromagnetic radiation or heat. When the electron returns to its original state, that energy is released as light.
What are 'Isotones' defined as in atomic physics?
Correct Answer: D. Atoms with the same number of neutrons
Isotones are different elements that share the exact same number of neutrons. For example, Carbon-14 and Oxygen-16 both contain 8 neutrons in their nuclei. They have different atomic numbers and different mass numbers.
Which scientist proposed the first modern atomic theory based on scientific evidence in 1803?
Correct Answer: C. John Dalton
John Dalton proposed that matter is made of indivisible atoms and that elements have unique masses. His theory laid the foundation for modern quantitative chemistry. Although some parts were later refined, his core concept of the atom remained vital.
The dual nature of matter (wave-particle duality) was proposed by which physicist?
Correct Answer: A. Louis de Broglie
Louis de Broglie suggested that all moving matter exhibits wave-like characteristics. This hypothesis was later confirmed by experiments involving electron diffraction. It is a cornerstone of the wave mechanical model of the atom.
Which region of the atom is responsible for chemical bonding and reactivity?
Correct Answer: C. Valence electrons
Valence electrons are located in the outermost shell of an atom. These are the electrons that are shared or transferred during chemical reactions. The number of valence electrons determines the chemical family to which an element belongs.
In the notation $_6C^{14}$, what does the number 14 represent?
Correct Answer: B. Mass number
The mass number is the sum of protons and neutrons in the nucleus. In this specific isotope of Carbon, there are 6 protons and 8 neutrons. This notation allows scientists to distinguish between different isotopes of the same element.
Which rule states that no two electrons in an atom can have the same set of four quantum numbers?
Correct Answer: A. Pauli Exclusion Principle
The Pauli Exclusion Principle ensures that each electron in an atom has a unique state. It implies that an orbital can hold a maximum of two electrons with opposite spins. This principle is vital for understanding the structure of the periodic table.
The 'Gold Foil Experiment' led to the discovery of which atomic feature?
Correct Answer: D. Nucleus
Ernest Rutherford observed that some alpha particles were deflected at large angles by gold atoms. This proved that most of the atom's mass is concentrated in a tiny, positive center. This center was subsequently named the nucleus.