Atom

Overview

An atom is the smallest unit of matter that retains the properties of an element. It consists of a dense nucleus containing protons and neutrons, surrounded by electrons in defined energy levels. Atoms combine to form molecules, making them the foundation of all chemical reactions and matter.

Questions and Answers

1. What is an atom according to John Dalton's atomic theory?

   According to John Dalton's atomic theory, an atom is the smallest particle of an element that can take part in a chemical reaction.

2. How are ions formed and what are their characteristics?

   Ions are formed when atoms lose or gain electrons, resulting in positively or negatively charged particles. They play a crucial role in chemical reactions and can be metals or non-metals.

3. Explain the concept of isotopes and provide examples.

   Isotopes are atoms of the same element with different numbers of neutrons. For example, carbon has isotopes like C-12, C-13, and C-14, each with the same number of protons but different neutrons.

4. How do isotopes contribute to the fractional atomic masses of elements?

   Isotopes with different atomic masses contribute to the fractional atomic masses of elements. The fractional atomic masses are calculated based on the relative abundance of each isotope present.

5. What is the relative abundance of isotopes and how is it determined?

   The relative abundance of isotopes refers to the percentage of each isotope in a naturally occurring sample of an element. Mass spectrometry is commonly used to determine the relative abundance of isotopes.

Multiple-Choice Questions

1. What is the smallest particle of an element that can take part in a chemical reaction?

   a) Molecule
   b) Atom
   c) Neutron
   d) Proton
   Answer: b) Atom

2. Who recognized the existence of atoms based on the law of conservation of matter and the law of definite proportions?

   a) Democritus
   b) John Dalton
   c) J. Berzelius
   d) Avogadro
   Answer: b) John Dalton

3. Which subatomic particles are considered fundamental particles of atoms?

   a) Electron, Proton, Neutron
   b) Hypron, Neutrino, Anti-neutrino
   c) Electron, Neutron, Hypron
   d) Proton, Neutrino, Anti-neutrino
   Answer: a) Electron, Proton, Neutron

4. What is the unit of relative atomic mass?

   a) Atomic Mass Unit (amu)
   b) Kilogram
   c) Gram
   d) Pound
   Answer: a) Atomic Mass Unit (amu)

5. Which particles are formed when atoms gain or lose electrons?

   a) Molecules
   b) Ions
   c) Neutrons
   d) Isotopes
   Answer: b) Ions