Chemical Elements, Bonding, Molecules and Nomenclature

Chemical Elements

1 Chemical elements

An elementary substance is made up of atoms from the same chemical element, while a chemical compound is made up of atoms from different chemical elements.

Names and Symbols of Chemical Elements

• Na — Sodium
• Sb — Antimony
• K — Potassium
• P — Phosphorus
• Fe — Iron
• S — Sulfur
• Ag — Silver
• Au — Gold

O — Oxygen (element)

O2 — Dioxygen (molecular oxygen)

O3 — Ozone

oxygen–carbon–oxygen = compound (substance)

oxygen–oxygen = elementary substance (pure substance)

Al = Aluminum (element)

Why Do Atoms Bond?

Atoms bond to become more stable. In other words, a group of bonded atoms is more stable than the separate atoms.

Example (energy): single bond > triple bond in many cases — N–N (single) corresponds to higher energy, N≡N (triple) corresponds to lower energy.

Molecules and Crystals

Molecules — a group containing a certain number of atoms, usually nonmetals.

Crystals — an ordered structure formed by the repetition of fundamental units.

Simple Substances

2 Types:

• Metals: like Na — Sodium; Cu — Copper
• Non-metals: like Ar — Argon; B — Boron

Formula, Traditional Nomenclature, Composition

• H2 — Hydrogen — Dihydrogen
• O2 — Oxygen — Dioxygen
• N2 — Nitrogen — Dinitrogen
• Cl2 — Chlorine — Dichlorine
• Br2 — Bromine — Dibromine
• O3 — Ozone — Trioxygen

Monoatomic Ions

• Na = Sodium (+1) — sodium ion (+1)
• Mg = Magnesium (+2) — magnesium ion (+2)

Note: Add charge notation to every ion.

Binary Compounds

Formula — Name with Multiplicative Prefix — Name with Oxidation State

• Na2O — sodium oxide (common name: sodium oxide)
• BaO — barium oxide
• Cu2O — copper(I) oxide (cuprous oxide)
• CO2 — carbon dioxide (carbon(IV) oxide)
• SO2 — sulfur dioxide (sulfur(IV) oxide)

Common names and corresponding systematic names with multiplicative prefixes:

• BH3 — borane — boron trihydride
• NH3 — ammonia — nitrogen trihydride
• H2O — water — dihydrogen oxide (common name: water)
• SiH4 — silane — silicon tetrahydride
• NaNO2 — sodium nitrite
• KNO2 — potassium nitrite

Calcium carbonate + heat → calcium oxide + carbon dioxide

Reaction: CaCO3 → CaO + CO2

• Na2O — sodium oxide
• NaOH — sodium hydroxide
• NaH — sodium hydride

Other Examples (Oxides, Halides, Sulfides, Selenides)

• SnO2 — tin dioxide — tin(IV) oxide
• V2O5 — vanadium pentoxide — vanadium(V) oxide
• HgCl2 — mercury(II) chloride (mercuric chloride)
• Na2S — sodium sulfide
• Fe2Se3 — iron(III) selenide
• NaBr — sodium bromide