Atomic Structure

Question 1

Atomic Number

Answer 1

The number of protons in a nucleus is called the atomic number and always equals the number of electrons in orbit about that nucleus (symbol Z)

Question 2

Mass Number

Answer 2

The total number of protons and neutrons in the nucleus of an atom.

Question 3

Ions

Answer 3

Atoms or molecules that have gained or lost electrons, resulting in a net positive or negative charge.

Question 4

Isotopes

Answer 4

Atoms of the same element that have the same number of protons but different numbers of neutrons, leading to different mass numbers.

the same chemical properties but different physical properties.

Question 5

Aufbau’s principle

Answer 5

States that electrons fill orbitals starting from the lowest energy level before moving to higher energy levels.

Question 6

Pauli exclusion Principle

Answer 6

States that no two electrons in an atom can have the same set of four quantum numbers, meaning an orbital can hold a maximum of two electrons with opposite spins.

Question 7

Hunds Rule

Answer 7

States that electrons will fill degenerate (equal-energy) orbitals singly before pairing up, to maximize the number of unpaired electrons.

Question 8

What are the exceptions for electron configuration

Answer 8

Some elements, like chromium (Cr) and copper (Cu), have electron configurations that deviate from the expected pattern to achieve greater stability by having half-filled or fully filled d-orbitals.

Chromium achieves greater stability by having half-filled d-orbitals (3d^5).
Copper achieves greater stability by having a fully filled d-orbital (3d^{10}).