Sir Folokiya

21/11/2025

nduodesa nkhuku ma17500 order kuyambira 5 kumakwela mmwamba ndipezeni kuchilobwe BT

14/11/2025

08/11/2025

Seconded

18/10/2025

⚛️ Aufbau Principle

Electrons fill atomic orbitals in the order of increasing energy levels, i.e., the lowest energy orbital is filled first before moving to higher ones.
👉 Example: 1s → 2s → 2p → 3s → 3p → 4s → 3d...
Mnemonic: "Aufbau" means "building up" in German.

⚛️ Hund’s Rule

When electrons occupy orbitals of the same energy (degenerate orbitals), they fill each orbital singly first with parallel spins before pairing up.
👉 This minimizes electron repulsion and increases stability.

⚛️ Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers.
👉 In a single orbital, two electrons must have opposite spins (↑↓).

18/10/2025

Mole Concept

The mole is a fundamental concept in chemistry used to count very small particles like atoms, molecules, or ions.

1 mole = 6.022 × 10²³ particles (Avogadro’s Number).
Example:
1 mole of H₂O = 6.022 × 10²³ molecules of water
1 mole of Na⁺ = 6.022 × 10²³ sodium ions

Molar Mass:
The mass of one mole of a substance, expressed in g/mol.
Example: H₂ = 2 g/mol, CO₂ = 44 g/mol

Relationship Between Mass and Moles:
Number of moles (n) = Given mass (g) ÷ Molar mass (g/mol)

Volume of Gases at STP (0°C, 1 atm):
1 mole of any gas = 22.4 L
n = Volume (L) ÷ 22.4

Empirical and Molecular Formula:
Empirical formula – simplest ratio of atoms.
Molecular formula – actual number of atoms in a molecule.

Limiting Reagent:
The reactant that gets completely used up and limits the amount of product formed.

Percentage Composition:
Percentage of element = (Mass of element in 1 mole ÷ Molar mass) × 100

18/10/2025

Basics of Organic Chemistry

18/10/2025

The periodic table of the elements is a chart that organizes all known chemical elements by their atomic number (the number of protons) in order of increasing atomic number. Elements are arranged in rows called periods and columns called groups, which are based on recurring chemical properties. This arrangement helps scientists understand the structure of atoms and predict how elements will behave in chemical reactions.

Key features

Atomic Number: Each element's position is determined by its atomic number, the number of protons in its nucleus. As you read the table from left to right, the atomic number increases by one with each element.

Groups: Vertical columns are called groups and contain elements with similar chemical properties, such as their electron configuration.

Periods: Horizontal rows are called periods. The number of electron shells in an atom determines its period number; for example, elements in period one have one electron shell.

Properties: The table's structure is based on the periodic law, which states that the properties of elements are periodic functions of their atomic numbers.
Element Categories: Elements are broadly categorized into metals, nonmetals, and metalloids, with metals on the left and nonmetals on the right, separated by a "staircase" of metalloids.

History: The modern periodic table evolved from earlier models, with Dmitri Mendeleev being credited with creating the framework in 1869, which included gaps for undiscovered elements.

16/10/2025

Once upon a time we had a president who ever fought Malawian taxes were church offerings and tithes....

Who had no knowledge on even simple family economics...