Unit 4: Atomic Bonding

Comprehensive vocabulary flashcards covering chemical formulas, molecular structures, valence electrons, Lewis dot diagrams, ionic bonding, and covalent bonding from Unit 4: Atomic Bonding.

Molecule

Two or more atoms that are chemically bonded (combined), which may consist of the same elements or different elements.

Compound

A substance formed from two or more different atoms that are chemically bonded (combined) in a fixed ratio; all compounds are molecules, but not all molecules are compounds.

Diatomic Element

A type of molecule made from two atoms of the same element naturally bonded to themselves in pairs, including hydrogen, oxygen, nitrogen, chlorine, fluorine, bromine, and iodine.

Chemical Formula

A combination of chemical symbols and numbers that represents the composition of a molecule or compound.

Coefficient

The large number placed in front of a chemical formula that shows the number of molecules and distributes to every element in the formula.

Subscript

The small number written behind an element in a chemical formula that indicates the number of atoms of that specific element; if absent, only $1$ atom of that element is present.

Parentheses ( ) in a Chemical Formula

A structural feature where a subscript placed outside the parentheses distributes to and multiplies every atom located inside the parentheses (such as in $Au(OH)_3$).

Valence Electrons

Electrons located in the outermost energy shell of an atom that determine the element's chemical properties and reactivity.

'Drop the One' Rule

A shortcut for elements in Groups $13$ through $18$ on the Periodic Table where dropping the initial digit '$1$' from the group number reveals the atom's number of valence electrons.

Helium's Valence Exception

Helium only has $2$ total electrons and a full $K$ shell with $2$ valence electrons, but it is classified in Group $18$ because its valence shell is completely full.

Ion

A charged particle that forms during a chemical change when one or more valence electrons transfer from one atom to another, resulting in a positive or negative charge.

Ionic Bond

A chemical bond formed between a metal and a nonmetal when electrons are transferred from one atom to another, producing oppositely charged ions that attract each other.

Covalent Bond

A chemical bond usually formed between nonmetals where atoms share valence electrons so that each atom attains a complete outer energy shell.

Chemical Stability (Magic Number 8)

The condition achieved when an atom possesses a complete set of valence electrons—specifically $8$ valence electrons for atoms with two or more shells, or $2$ valence electrons for atoms with one shell.

Alkali Metals (Bonding Pattern)

Group $1$ metals that readily lose $1$ electron to form $+1$ ions, frequently bonding with halogens to form ionic compounds.

Halogens (Bonding Pattern)

Group $17$ nonmetals that gain $1$ electron to form $-1$ ions; they are the most reactive nonmetals on the periodic table, with fluorine being the most reactive.

Noble Gases (Bonding Behavior)

Group $18$ elements that do not form chemical bonds because their valence electron shells are already full and chemically stable.