Definitions [10]
Define the term ‘mass number’ of an atom.
Mass number of an element is equal to the sum of protons and neutrons in the nucleus of the atom.
Define the following form:
Atomic number
The number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table. Atomic number is also equal to numbers of electrons in an atom.
For example:
- Atomic number of carbon = 6
- Atomic number of nitrogen = 7
- Atomic number of oxygen = 8
- Atomic number of magnesium = 12
Define the term ‘atomic number’ of an atom.
Atomic number is the number of protons in the atom of an element.
The atoms of the same element, having same atomic number Z, but different mass number A, are called isotopes.
OR
Atoms having the same atomic number (Z) but different mass numbers (A).
The mass number of an atom is equal to the total number of nucleons (i.e., the sum of the number of protons and the number of neutrons) in its nucleus.
Define the term atomic number.
The number of protons in the nucleus is known as the atomic number of the element and is denoted by Z.
Define the term mass number.
The total number of neutrons and protons in the nucleus is called the mass number of the element and is denoted by A.
The atomic number of an atom is equal to the number of protons in its nucleus (which is same as the number of electrons in a neutral atom).
Define photoelectric effect.
The phenomenon of emission of electrons from a metal surface when radiation of appropriate frequency is incident on it is known as the photoelectric effect.
Define the term Electronic configuration.
Electronic configuration of an atom is defined as the distribution of its electrons in orbitals.
Key Points
- The structure of an atom and its nucleus was developed from the discovery of electrons by J.J. Thomson and alpha particle scattering experiments by Rutherford.
- An atom consists of electrons, protons, and neutrons, with protons and neutrons in the nucleus and electrons revolving in stationary orbits.
- The maximum number of electrons in a shell is given by 2n², and the shells are named K, L, M, N, O, P, and Q.
Concepts [31]
- History of Atom
- Electrons (e)
- Protons (p)
- Neutrons (n)
- Atomic Models
- J. J. Thomson’s Atomic Model
- Lord Rutherford’s Atomic model
- Drawbacks of Rutherford Atomic Model
- Atomic Number (Z) and Mass Number (A)
- Isotopes
- Isoelectronic Species
- Structure of the Atom and Nucleus
- Wave Nature of Electromagnetic Radiation
- Newton's corpuscular theory
- Qualitative Ideas of Black Body Radiation
- Particle Nature of Electromagnetic Radiation: Planck's Quantum Theory of Radiation
- The Photoelectric Effect
- Towards Quantum Mechanical Model of the Atom
- Dual Behaviour of Matter: De Broglie's relationship
- Heisenberg’s Uncertainty Principle
- Evidence for the Quantized Electronic Energy Levels - Atomic Spectra
- Neils Bohr’s Model of an Atom
- Bohr’s Model for Hydrogen Atom
- Quantum Mechanical Model of Atom
- Quantum Mechanical Model of the Atom - Concept of Shells and Subshells
- Quantum Mechanical Model of the Atom - Orbitals and Quantum Numbers
- Quantum Mechanical Model of the Atom - Shapes of Atomic Orbitals
- Quantum Mechanical Model of the Atom - Energies of Orbitals
- Quantum Mechanical Model of the Atom - Filling of Orbitals in Atom
- Quantum Mechanical Model of the Atom - Electronic Configuration of Atoms
- Quantum Mechanical Model of the Atom - Stability of Completely Filled and Half Filled Subshells
