Carbon and its Compounds - Covalent Bonding and Allotropes

Vocabulary flashcards covering the concepts of carbon abundance, covalent bonding, electronic configuration, physical properties of carbon compounds, and carbon allotropes (diamond, graphite, and fullerenes).

Carbon Abundance in Earth's Crust

Accounts for $0.02\%$ of the Earth's crust, occurring in the form of minerals such as carbonates, hydrogen-carbonates, coal, and petroleum.

Carbon Abundance in the Atmosphere

Accounts for $0.03\%$ of the atmosphere in the form of carbon dioxide.

Ionic Compounds

Compounds formed by the gain or loss of electrons that have high melting and boiling points and conduct electricity in aqueous solution or in the molten state.

Electrical Conductivity of Carbon Compounds

Carbon compounds are largely non-conductors or poor conductors of electricity because bonding occurs by sharing electrons and does not give rise to any ions.

Melting and Boiling Points of Acetic Acid ($CH_3COOH$)

Possesses a melting point of $290\,K$ and a boiling point of $391\,K$.

Melting and Boiling Points of Chloroform ($CHCl_3$)

Possesses a melting point of $209\,K$ and a boiling point of $334\,K$.

Melting and Boiling Points of Ethanol ($CH_3CH_2OH$)

Possesses a melting point of $156\,K$ and a boiling point of $351\,K$.

Melting and Boiling Points of Methane ($CH_4$)

Possesses a melting point of $90\,K$ and a boiling point of $111\,K$.

Reactivity of Elements

The tendency of atoms of elements to attain a completely filled outer shell, achieving a stable noble gas configuration.

Electronic Configuration of Carbon

Carbon has an atomic number of $6$, meaning it has $4$ electrons in its outermost shell and requires $4$ more electrons to achieve noble gas configuration.

$C^{4-}$ Anion Formation Difficulty

If carbon were to gain four electrons, it would be extremely difficult for its nucleus with $6$ protons to hold on to $10$ electrons ($4$ extra electrons).

$C^{4+}$ Cation Formation Difficulty

Removing four electrons from carbon would require a very large amount of energy, leaving behind a cation with $6$ protons holding on to just $2$ electrons.

Covalent Bond

A chemical bond formed by the sharing of one or more electron pairs between two atoms so that both achieve a noble gas configuration.

Single Covalent Bond

A bond constituted by a single shared pair of electrons between two atoms, represented by a single line (such as between two hydrogen atoms in $H_2$).

Double Covalent Bond

A bond constituted by two shared pairs of electrons between two atoms, as formed between two oxygen atoms ($O_2$), each having an atomic number of $8$ and needing $2$ electrons to complete its octet.

Triple Covalent Bond

A bond constituted by three shared pairs of electrons between two atoms, as formed between two nitrogen atoms ($N_2$), each having an atomic number of $7$ and contributing $3$ electrons to complete its octet.

Tetravalent

The property of an atom, such as carbon, having a valency of $4$ because it possesses four valence electrons available for sharing.

Methane ($CH_4$)

The simplest carbon compound, containing carbon covalently bonded to four hydrogen atoms; it is widely used as a fuel and serves as a major component of bio-gas and Compressed Natural Gas (CNG).

Physical Properties of Covalently Bonded Molecules

Molecules with strong internal covalent bonds but weak intermolecular forces between molecules, resulting in comparatively low melting and boiling points.

Allotropes of Carbon

Different natural elemental forms of carbon that share identical chemical properties but possess widely varying physical properties due to differences in how carbon atoms are bonded together.

Diamond

An allotrope of carbon in which each carbon atom is bonded to four other carbon atoms to form a rigid three-dimensional structure; it is the hardest substance known.

Graphite

An allotrope of carbon where each carbon atom is bonded to three other carbon atoms in the same plane to form hexagonal arrays in layers; it contains a double bond, is smooth and slippery, and conducts electricity well.

Synthetic Diamonds

Small diamonds synthesised by subjecting pure carbon to very high pressure and temperature, which are otherwise indistinguishable from natural diamonds.

Fullerenes

A class of carbon allotropes; the first identified was $C-60$, which features carbon atoms arranged in the shape of a football and is named after the US architect Buckminster Fuller.