Understanding Atoms, Elements, and Bonds in Chemistry

Atom

The smallest particles a simple substance can be divided into without losing its chemical properties.

Chemical Element

A chemical element is a species of atoms having the same number of protons in their atomic nuclei.

Subatomic Particles

• Electrons: negative charge, no mass
• Protons: positive charge, mass
• Neutrons: no charge, mass equal to protons.

Atomic Models

• Plum Pudding Model: a sphere of positive electricity with neutrons
• Rutherford's: each electron had an orbit
• Bohr's: each orbit presents a different number of electrons.

To differentiate an atom from others, the number of protons and neutrons it has in its nucleus.

Atomic Number

Number of protons in the nucleus of an atom (Z).

Mass Number

The number of protons and neutrons in the nucleus of an atom (A).

Isotopes

Varieties of atoms with the same atomic number but different mass number. They have a different number of neutrons in their nucleus. We differentiate them by their mass number.

Ions

Atoms that gain or lose electrons in their shells. Cations are positive, and anions are negative.

Metals

Shiny, room temperature solid (except mercury), conductors of heat and electricity.

Non-Metals

No shine, solid, liquid, and gas, not conductors of heat or electricity.

Bonds

Union between atoms. Noble gases do not form bonds. Different types of bonds:

• Covalent: non-metal, non-metal, molecule, crystalline lattice
• Ionic: non-metal, metal, crystalline lattice
• Metallic: metal, metal, crystalline lattice

Molecule: the smallest unit of a pure substance that conserves all its properties. Formed when a number of non-metal atoms form a bond. The state of the substance formed could be solid (sulfur), liquid (water), or gas (nitrogen).

Crystals: groups of atoms ordered in a geometric structure.

Crystal Unit Cells: the smallest block in the crystal.

Types of Crystals

• Covalent: not soluble in water, high melting point, not conductive
• Ionic: soluble in water, high melting point, conductive when melted or dissolved
• Metallic: not soluble in water, melting point varies, conductive