Chemistry 1st Trimester Final Exam Review Material Chapter 2 – Matter and Change 2.1 – Properties of Matter Properties used to describe matter can be classified as extensive or intensive. Every sample of a given substance has identical intensive properties because every sample has the same composition. Three states of matter are solid, liquid, and gas. Physical changes can be classified as reversible or irreversible. 2.2 – Mixtures Mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures, based on the distribution of their components. Differences in physical properties can be used to separate mixtures. 2.3 – Elements and Compounds Compounds can be broken down into simpler substances by chemical means, but elements cannot. If the composition of a material is fixed, the material is a substance. If the composition may vary, the material is a mixture. Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds. 2.4 – Chemical Reactions During a chemical change, the composition of matter always changes. Four possible clues to chemical change include a transfer of energy, a change in color, the production of a gas, or the formation of a precipitate. During any chemical reaction, the mass of the products is always equal to the mass of the reactants. Vocabulary: Chemical change Chemical Property Chemical Reaction Chemical symbol Compound Distillation Element Extensive Property Filtration Gas Heterogeneous Mixture Homogeneous Mixture Intensive Property Law of Conservation of Mass Liquid Mass Mixture Phase Physical change Physical Property Precipitate Product Reactant Solid Solution Substance Vapor Volume Chapter 5 – Electrons in Atoms 5.1 – Models of the Atom Rutherford’s planetary model couldn’t explain the chemical properties of elements. Bohr proposed that electrons move only in specific circular paths, or orbits, around the nucleus. Chemistry 1st Trimester Final Exam Review Material 5.2 – Electron Arrangement in Atoms Three rules – the aufbau principle, the Pauli-exclusion principle, and Hund’s rule – tell you how to find the electron configurations of atoms. Vocabulary: Atomic Orbital Aufbau Principle Electron Configurations Energy Levels Hund’s Rule Pauli exclusion principle Chapter 6 – The Periodic Table 6.1 – Organizing the Elements Chemists used the properties of elements to sort them into groups. Menmdeleev arranged the elements in his periodic table in order of increasing atomic mass. In the modern periodic table, elements are arranged in order of increasing atomic number, The elements within a group in the table have similar properties. Three classes of elements are metals, non-metals, and metalloids. 6.2 – Classifying the Elements The periodic table displays the symbols and names of elements, along with information on the structure of their atoms. Elements can be sorted into noble gases, representative elements, transition metals, or inner transition metals based on their electron configurations. The periodic table can be divided into s, p, d, and f blocks that correspond to the highest occupied sublevels in atoms of elements. 6.3 – Periodic Trends In general, atomic size increases from top to bottom within a group and decreases from left to right across a period. Positive and negative ions form when electrons are transferred between atoms. First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period. Cations are always smaller than the atoms from which they form. Anions are always larger than the atoms from which they form. In general, electronegativity values decreases from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period. Trends in atomic size, ionization energy, ionic size, and electronegativity can be explained by variations in atomic structure. The increase in nuclear charge within groups and across periods explains many trends. Within groups an increase in shielding has a significant effect. Vocabulary: Alkali Metals Alkaline Earth Metals Anion Atomic Radius Cation Electronegativity Halogens Inner Transition Metal Ion Ionization Energy Metalloids Metals Noble Gases Nonmetals Periodic Law Representative Elements Transition Metal Chemistry 1st Trimester Final Exam Review Material Chapter 7 – Ionic and Metallic Bonding 7.1 – Ions To find the number of valence electrons in an atom of a representative element, simply look at its group number. Atoms of the metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetallic elements tend to gain electrons to achieve a complete octet. An atom’s loss of valence electrons produces a positively charged cation. The gain of electrons by a neutral atom produces a negatively charged anion. 7.2 – Ionic Bonds and Ionic Compounds Although they are composed of ions, ionic compounds are electrically neutral. Most ionic compounds are crystalline solids at room temperature, and they generally have high melting points. Ionic compounds can conduct an electric current when melted or dissolved in water. 7.3 – Bonding in Metals The valence electrons of metal atoms can be modeled as a sea of electrons. Metal atoms are arranged in very compact and orderly patterns. Alloys are important because their properties are often superior to those of their component elements. Vocabulary: Alloys Chemical Formula Electron Dot Structure Formula Unit Halide Ion Ionic Bonds Ionic Compounds Metallic Bonds Octet Rule Valence Electron Chapter 8 – Covalent Bonding 8.1 – Molecular Compounds Molecular compounds tend to have relatively low melting and boiling points. A molecular formula shows how many atoms of each element a molecule contains. 8.2 – The Nature of Covalent Bonding Electron sharing occurs so that atoms attain the configurations of noble gases. An electron dot structure shows the shared electrons of a covalent bond by a pair of dots. Atoms form double or triple bonds by sharing two or three pairs of electrons. In a coordinate covalent bond, the shared electron pair comes from a single atom. A large bond dissociation energy corresponds to a strong covalent bond. In ozone, the bonding of oxygen atoms is a hybrid of the extremes represented by the resonance forms. The octet rule is not satisfied in molecules with an odd number of electrons, and in molecules where an atoms has less, or more, than a complete octet of valence electrons. 8.3 – Bonding Theories Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole. According to VSEPR theory, the repulsion between electron pairs causes moledular shapes to adjust so that the valence-electron pairs stay as far apart as possible. Chemistry 1st Trimester Final Exam Review Material Orbital hybridization provides information about both molecular bonding and molecular shape. 8.4 – Polar Bonds and Molecules When different atoms bond, the more electronegative atom attracts electrons more strongly and acquires a slight negative charge. Polar molecules between oppositely charged metal plates tend to become oriented with respect to the positive and negative plates. Intermolecular attractions are weaker than either an ionic or covalent bond. Melting a network solid requires breaking covalent bonds throughout the solid. Vocabulary: Bond Dissociation Energy Bonding Orbital Covalent Bond Coordinate Covalent Bond Diatomic Molecule Dipole Dipole Interactions Dispersion Forces Double Covalent Bond Hybridization Hydrogen Bonds Molecular Compound Molecular Formula Molecular Orbital Molecule Network Solids Nonpolar Covalent Bond Pi Bond Polar Bond Polar Covalent Bond Polar Molecule Polyatomic Ion Resonance Structure Sigma Bond Single Covalent Bond Structural Formula Tetrahedral Angle Triple Covalent Bond Unshared Pair VSEPR Theory