Atomic Structure and Chemical Bonds: A Deep Dive

Posted on Mar 17, 2025 in Chemistry

Atomic Structure

Electron: A very light particle with a negative charge, moving complexly around the nucleus.
Proton: A particle with a positive charge, equal in magnitude to that of the electron. It is found in the atomic nucleus, and its mass is much higher than that of the electron.
Neutron: An electrically neutral particle with a mass similar to that of the proton. It is also found inside the atomic nucleus.

Atomic Number (Z): The number of protons an atom has. Since atoms are electrically neutral, the number of electrons must be equal to the atomic number.
Mass Number (A): The number obtained by adding the atomic number and the number of neutrons an atom has in its nucleus (A = Z + N, where N is the number of neutrons, N = A – Z).
Isotopes: Atoms with the same atomic number but different mass numbers. Having the same atomic number means they are atoms of the same chemical element. The difference in mass number indicates they have different numbers of neutrons.
Atomic Mass of an Element: The weighted average of the atomic masses of the isotopes. The mass number indicates the approximate atomic mass of each isotope.
Ions: When an atom gains or loses an electron, it becomes a charged particle called an ion. If there has been a loss of electrons, the ion is positively charged and is called a cation. Otherwise, it will have a negative charge and is called an anion.
Elements: Basic substances that make up all matter; they cannot be broken down into simpler substances.

Chemical Bond: Different ways in which atoms unite.
Ionic Bond: An electrical attraction between ions of opposite signs. It occurs between a metal and a nonmetal.
Covalent Bond: The sharing of pairs of electrons. In each shared pair, one electron belongs to one atom and the other belongs to the second atom. It combines two atoms of a nonmetal.

Covalent Solid: A minority group of substances with covalent bonds.
Nonpolar Covalent Bond: Occurs between atoms that attract the pair of electrons equally. This happens when the two atoms are identical. Example: H₂, N₂, O₂, Cl₂.
Polar Covalent Bond: Occurs between different atoms. Examples: HCl, NH₃. If the geometry of the molecule has great symmetry, polar bonds can be offset with each other and form nonpolar molecules.
Octet Rule: In the formation of a compound, atoms exchange or share electrons to get eight valence electrons.
Metallic Bond: Occurs between atoms of one or more metals. It leads to a network called a metallic lattice. In this network, the nodes are cations.
Mole: Amount of matter that has a number of particles equal to Avogadro’s number.

Type of Substance	Example	Melting Point (Tª)	H₂O Solubility	Electrical Conductivity (Eª)
Ionic	KCl, MgF₂	High	High	High if melted or dissolved
Polar Covalent	H₂O	Low	High	Low
Nonpolar Molecular	CO₂	Very Low	Very Low	Very Low
Covalent Solid	Diamond, SiO₂	Very High	None	Very Low
Metallic	Mg, Cu	Medium	Very Low	Very High

Group 1 (Alkali Metals): Hydrogen (H): 1s¹, Lithium (Li): 1s²2s¹, Sodium (Na): 1s²2s²2p⁶3s¹, Potassium (K): 1s²2s²2p⁶3s²3p⁶4s¹
Group 2 (Alkaline Earth Metals): Beryllium (Be): 1s²2s², Magnesium (Mg): 1s²2s²2p⁶3s², Calcium (Ca): 1s²2s²2p⁶3s²3p⁶4s²
Group 16 (Chalcogens): Oxygen (O): 1s²2s²2p⁴, Sulfur (S): 1s²2s²2p⁶3s²3p⁴, Selenium (Se): 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴
Group 17 (Halogens): Fluorine (F): 1s²2s²2p⁵, Chlorine (Cl): 1s²2s²2p⁶3s²3p⁵, Bromine (Br): 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁵