Atomic Nucleus, Electron Orbits,

Question 1

What is the Rutherford model of the atom?

Answer 1

In 1911, Rutherford described the atom as consisting of a small, positively charged nucleus surrounded by negatively charged electrons moving in defined orbits.

Question 2

What determines the mass and charge of an atomic nucleus?

Answer 2

The number of protons and neutrons (nucleons) in the nucleus determines its mass and charge.

Question 3

Define nucleon, atomic number, and atomic mass number.

Answer 3

Nucleon: A proton or neutron within the nucleus.
Atomic number (Z): Number of protons in the nucleus.
Atomic mass number (A): Total number of nucleons in the nucleus.

Question 4

What is an isotope?

Answer 4

Isotopes are members of an element’s family with the same number of protons but different numbers of neutrons.

Question 5

What is a radionuclide? Provide an example.

Answer 5

A radionuclide is a radioactive nuclide. Example: Carbon-14 undergoes beta decay by emitting electrons from the nucleus.

Question 6

How do electrons arrange themselves around the nucleus?

Answer 6

Electrons orbit the nucleus in discrete paths or shells, filling inner shells first due to their lower energy.

Question 7

What is the principal quantum number?

Answer 7

The principal quantum number 𝑛 indicates the shell number, starting from 𝑛=1 for the K shell.

Question 8

What determines an atom’s chemical activity and mass?

Answer 8

Chemical activity: Determined by electrons in the outer orbit.
Mass: Determined by the nucleus.

Question 9

What is the maximum number of electrons per shell?

Answer 9

The maximum number of electrons in a shell is given by 2n power 2
.

Question 10

What is valency?

Answer 10

Valency is the ability of an atom to bond with another atom, determined by the number of electrons in the outer shell.

Question 11

Differentiate between ionic and covalent bonds.

Answer 11

• Ionic bond: Formed when an electron is transferred from one atom to another, creating charged ions.
• Covalent bond: Formed by sharing electrons, leading to a stable electron configuration.

Question 12

What happens during electron excitation and ionization?

Answer 12

• Excitation: An electron absorbs energy and moves to a higher-energy orbit.
• Ionization: An electron absorbs enough energy to escape the atom completely.

Question 13

What is the photoelectric effect?

Answer 13

The photoelectric effect occurs when a photon is absorbed, ejecting an electron from the atom.

Question 14

Define electron binding energy.

Answer 14

• The energy required to remove an electron from an atom, measured in electron volts (eV).
• It depends on the atomic number and distance from the nucleus.

Question 15

How does the binding energy of electrons vary?

Answer 15

• Increases with atomic number (Z).
• Decreases with distance from the nucleus (inner-shell electrons have greater binding energy).

Question 16

What happens when an inner-shell electron is ejected?

Answer 16

• The vacancy is filled by an outer-shell electron, and the excess energy is emitted as electromagnetic radiation.