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Indietro

Chapter 4

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Termini in questo insieme (30)

  • What is a molecule?
    A molecule is formed when two or more nonmetallic elements combine, either the same or different elements.
  • What does the Law of Definite Proportion state?
    A compound always contains the same proportion of elements by mass; for example, water always has 2 hydrogen atoms for every 1 oxygen atom.
  • What are the two main types of chemical bonds?
    Ionic bonds, which involve electron transfer between metals and nonmetals, and covalent bonds, which involve electron sharing between nonmetals.
  • How do ionic bonds form?
    Ionic bonds form when a metal transfers electrons to a nonmetal, creating cations and anions that attract electrostatically.
  • What characterizes covalent bonds?
    Covalent bonds occur between nonmetal atoms sharing electrons, forming molecules called molecular compounds.
  • What is the difference between empirical, molecular, and structural formulas?
    Empirical formulas show the simplest whole-number ratio of atoms, molecular formulas show the actual number of atoms, and structural formulas show how atoms are bonded.
  • What is a Lewis structure?
    A diagram showing valence electrons as dots around atoms, illustrating bonding and lone pairs in molecules.
  • What is the octet rule?
    Atoms tend to gain, lose, or share electrons to have eight valence electrons, achieving a noble gas configuration.
  • What are exceptions to the octet rule?
    Hydrogen follows a duet rule (2 electrons), and some period 3 or heavier elements can have expanded octets using d-orbitals.
  • What is a formula unit in ionic compounds?
    The smallest electrically neutral ratio of ions in an ionic compound, which exists as a crystal lattice rather than discrete molecules.
  • What is lattice energy?
    The energy released when a crystal lattice forms from gaseous ions; it stabilizes ionic compounds and is always exothermic.
  • Why do ionic solids conduct electricity only when molten or dissolved?
    Because ions are fixed in place in solids but free to move in liquid or aqueous states, allowing electrical conductivity.
  • How are ionic compound formulas determined?
    By balancing the total positive and negative charges of the ions to get the smallest whole-number ratio.
  • What distinguishes type one and type two metals in ionic compounds?
    Type one metals have invariant charges; type two metals (transition metals) have variable charges indicated by Roman numerals in names.
  • How are binary ionic compounds named?
    Name the cation first, then the anion with an -ide suffix; for type two metals, include the cation charge in Roman numerals.
  • What are polyatomic ions?
    Charged species composed of two or more atoms covalently bonded, acting as a single ion in compounds.
  • How are hydrates named?
    By naming the ionic compound followed by a prefix indicating the number of water molecules and the word 'hydrate'.
  • What is the difference between bonding pairs and lone pairs?
    Bonding pairs are shared electrons forming covalent bonds; lone pairs are valence electrons not involved in bonding.
  • What are single, double, and triple covalent bonds?
    Single bonds share one pair of electrons, double bonds share two pairs, and triple bonds share three pairs between atoms.
  • How do molecular compounds differ from ionic compounds?
    Molecular compounds consist of discrete molecules with covalent bonds, while ionic compounds form extended lattices of ions.
  • How are molecular compounds named?
    Using prefixes to indicate the number of atoms of each element, with the element of lower group number named first.
  • What is molecular mass?
    The sum of the atomic masses of all atoms in a molecule or formula unit.
  • How is molar mass used to count molecules?
    Convert mass to moles using molar mass, then multiply by Avogadro's number to find the number of molecules.
  • How is mass percent composition calculated?
    By dividing the mass of an element in a compound by the total mass of the compound and multiplying by 100%.
  • How can chemical formulas be used as conversion factors?
    They relate moles of elements to moles of compounds, allowing conversion between masses of elements and compounds.
  • What is the empirical formula?
    The simplest whole-number ratio of atoms in a compound, determined from experimental data like percent composition.
  • How is an empirical formula determined from percent composition?
    Convert percent to grams, then to moles, divide by smallest mole value, and multiply to get whole numbers.
  • How is the molecular formula related to the empirical formula?
    The molecular formula is a whole-number multiple of the empirical formula, determined using molar mass.
  • What is combustion analysis used for?
    Determining empirical formulas of organic compounds by burning and measuring masses of combustion products.
  • What is unique about carbon bonding?
    Carbon forms four covalent bonds and can create long chains and rings, making it central to organic chemistry.