Chemistry

Chemical Bonding

• Atoms can lose or gain electrons to achieve a full outer electron shell, similar to the nearest noble gas
• Losing electrons results in a positively charged ion (cation), while gaining electrons results in a negatively charged ion (anion)
• Ionic bonds form through electrostatic attraction between oppositely charged ions
• Ionic compounds have high melting and boiling points, are brittle, and can conduct electricity when molten or dissolved in water

Ionic Compounds

• Form solid crystals at room temperature
• Have high melting and boiling points due to strong electrostatic forces between ions
• Properties related to structure, requiring significant energy to break

Covalent Bonds

• Form when two non-metal atoms share one or more pairs of electrons
• Molecular structure involves atoms bonded by shared electrons in discrete molecules
• Properties of covalent compounds include lower melting and boiling points, poor electrical conductivity, and varying solubility in water

Giant Covalent Molecules

• Have very high melting and boiling points due to strong covalent bonds in a vast network
• Examples include diamond and silicon dioxide
• Most giant covalent structures do not conduct electricity, but graphite is an exception due to delocalized electrons

Metallic Bonding

• Metals consist of a lattice of positively charged metal ions immersed in a "sea" of delocalized valence electrons
• Metal atoms are arranged in a regular, repeating pattern, forming a crystal lattice
• Properties include high electrical and thermal conductivity, malleability, and ductility

Alloys

• Substitutional alloys: atoms of one metal replace atoms of another in the crystal lattice (e.g., brass)
• Interstitial alloys: smaller atoms fit into spaces between larger atoms in the crystal lattice (e.g., steel)

Allotropes

• Different structural forms of the same element in the same physical state
• Examples of carbon allotropes: diamond, graphite, graphene, and fullerenes
• Each allotrope has distinct physical and chemical properties due to different arrangements of carbon atoms

Stoichiometry

• Avogadro's number: 6.02 x 10^23, representing the number of atoms, ions, or molecules in one mole of a substance
• Formula: # particles = n x N
• Molar mass: the mass of one mole of a substance, typically expressed in grams per mole (g/mol)
• Mole: the amount of any chemical substance that contains the same number of particles as there are in 12 grams of pure carbon-12 (12C)