Test: Atomic Structure and Chemical Bonding - Class 9 MCQ

Chadwick discovered the neutron, a neutral particle that has a mass roughly equal to that of a proton. This discovery was crucial for understanding atomic structure and nuclear reactions.

Noble gases are non-reactive because their outermost electron shell is full, which makes them stable and unlikely to participate in chemical reactions to gain or lose electrons.

The L shell can hold a maximum of 8 electrons, calculated using the formula 2n² where n is 2 for the L shell. This arrangement is crucial for the stability and reactivity of atoms.

Democritus is known for introducing the term "atom," derived from the Greek word meaning "indivisible." This concept was significant in the development of atomic theory in ancient philosophy.

J.J. Thomson is credited with the discovery of the electron through his experiments with cathode rays, concluding that they were composed of negatively charged particles.

An example of isobars is Carbon-12 and Carbon-14, which have the same mass number (14) but different atomic numbers, as they differ in the number of protons.

Maharshi Kanada introduced the concept of "paramanu," which refers to the smallest, indivisible particles of matter, similar to what we now call atoms. This foundational idea laid the groundwork for later atomic theories.

Rutherford's gold foil experiment revealed that atoms consist mostly of empty space, with a dense, positively charged nucleus at the center. This was a pivotal moment in atomic theory.

An element is defined as a pure substance that consists entirely of one type of atom and cannot be broken down into simpler substances by ordinary chemical means.

The K shell can hold a maximum of 2 electrons, according to the formula 2n², where n is the shell number. This is fundamental to understanding electron configuration in atoms.

A proton carries a positive charge. The positive charge of protons in the nucleus contributes to the overall charge of an atom, balancing the negative charge of electrons.

Valence electrons are crucial because they determine an atom's chemical properties and reactivity. Atoms tend to gain, lose, or share electrons to achieve a stable electronic configuration.

The electron dot structure (or Lewis structure) represents the valence electrons of an atom, providing insight into how atoms might bond with each other during chemical reactions.

Dalton's Atomic Theory posits that atoms combine in simple whole-number ratios to form compounds. This principle is foundational in understanding chemical reactions and stoichiometry.

The atomic number of an element is defined by the number of protons in its nucleus. This number determines the element's identity and its position on the periodic table.

Ionic compounds are stable due to the strong electrostatic attraction between positively and negatively charged ions. This attraction overcomes the repulsive forces between ions of the same charge.

HCl (hydrogen chloride) has polar covalent bonds because the shared electrons are drawn closer to the chlorine atom, creating a dipole moment with partial positive and negative charges.

Bohr proposed that electrons move in fixed orbits around the nucleus, each with a specific energy level, which explains the stability of atoms and the quantized nature of energy levels.

Isotopes are defined as atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers while retaining identical chemical properties.

A covalent bond is formed when two or more atoms share pairs of electrons. This type of bonding is common between non-metal atoms and is essential for forming molecules.