Chemistry: Metals, Nonmetals, and Ions

Metals

• Good conductors of heat and electricity
• Shiny (lustrous)
• Malleable (can be shaped)
• Tend to lose electrons in chemical reactions (form cations)

Nonmetals

• Poor conductors of heat and electricity
• Not shiny (dull)
• Not malleable (brittle)
• Tend to gain electrons in chemical reactions (form anions)

Metalloids

• Properties intermediate between metals and nonmetals
• Can be good or bad conductors of heat and electricity depending on conditions (semiconductors)

Ions

• Atoms or molecules with a net positive or negative charge due to the loss or gain of electrons
• Cations: Positively charged ions
• Anions: Negatively charged ions

Molecules

• Two or more atoms held together by chemical bonds

Ionic Compounds

• Generally formed by metals and nonmetals
• Ions arranged in a 3D structure
• Total positive charge must equal total negative charge
• The net charge of the cation and anion determine the subscript of each element in the compound (e.g., NaCl - charges of 1+ and 1- so subscripts are 1)

Molecular Compounds

• Contain more than one type of atom
• Mostly composed of nonmetals
• Atoms share electrons (covalent bonds)
• Generally have lower melting and boiling points than ionic compounds

Empirical Formulas

• Represent the simplest whole-number ratio of atoms in a compound
• Provide the relative number of atoms of each type in a molecule
• Subscripts are the smallest possible whole numbers

Molecular Formulas

• Indicate the actual number of atoms in a molecule
• Not always the same as empirical formula (e.g., H₂O₂ (molecular formula) and HO (empirical formula))

Naming Compounds

• Subscripts and superscripts are used to represent specific information about an element in a compound
• Atomic number is written as a subscript on the left of the element symbol
• Mass number is written as a superscript on the left of the element symbol
• Ionic charge is written as a superscript on the right of the element symbol (if charge is 0, nothing is written)
• If the charge is +1 or -1, only the + or - sign is written
• If the charge is +2, +3, -2, or -3, the number followed by the sign is written

Electron Transfer

• Atoms gain or lose electrons to achieve a noble gas configuration (stable electron configuration)
• Example: Sodium (Na) loses one electron to form Na⁺ (cation) and Chlorine (Cl) gains one electron to form Cl^- (anion)

Ionic Bonds

• Electrostatic force of attraction between oppositely charged ions
• Example: Na⁺ and Cl^- form NaCl

Properties of Ionic Compounds

• High melting and boiling points
• Conduct electricity when dissolved in water or molten

Covalent Bonds

• Sharing of electron pairs between atoms
• Example: Water (H₂O) formed by sharing electrons between hydrogen and oxygen atoms

Stoichiometry of Compounds

• Empirical and molecular formulas provide information about the ratio and actual number of atoms in a compound