Non-Metallic Substances, Elements, Compounds, and Covalent Bonding

Element: A substance that cannot be further divided into simpler substances by chemical methods; all the atoms of an element contain the same number of protons.
Metals: A class of chemical elements (and alloys) that all have a characteristic shiny appearance and are good conductors of heat and electricity.
Non-metals: A class of chemical elements that are typically poor conductors of heat and electricity.
Compound: A substance formed by the chemical combination of two or more elements in fixed proportions.

Elements are the fundamental building blocks of the universe, with each element possessing its own distinctive physical and chemical properties.
Element reactivity varies across a broad spectrum:
- Certain elements are extremely reactive.
- Noble gases, located in Group VIII of the Periodic Table, are extraordinarily stable and chemically inert.
Total number of known elements exceeds $100$ , with exactly $94$ occurring naturally.
Elements are fundamentally categorized into two primary divisions: metals and non-metals.
Atomic composition within an element:
- All atoms of a specific element are identical in terms of their proton and electron content.
- Every atom of a given element possesses the exact same atomic number, distinguishing it entirely from the atoms of any other element.

Elements undergo chemical bonding to create all compounds in existence, spanning from basic substances to complex biological molecules.
Every chemical compound consists of specific elements bound together in fixed, definite proportions.
Examples of fundamental chemical compounds include:
- Water: Each molecule consists of two hydrogen atoms bonded to a single oxygen atom.
- Ammonia
- Methane

Upon reacting to form a chemical compound, elements forfeit their individual characteristic properties, which are replaced by the distinct properties of the resulting compound.
The physical and chemical properties of a compound bear no direct relationship or resemblance to the properties of the elements from which it is formed.
Case Study - Sodium Chloride (Common Salt):
- Elemental Sodium: A highly reactive metal that reacts violently on contact with water, producing sufficient heat to potentially trigger a flame.
- Elemental Chlorine: A toxic gas previously deployed as a chemical weapon, which continues to be utilized for eradicating harmful microbes in water treatment facilities.
- Sodium Chloride Compound: The resulting compound formed from sodium and chlorine yields common table salt, displaying none of the hazardous characteristics of its constituent elements.