Atomic Structure and Bonding

Atomic Structure and Bonding

• Atoms are the fundamental units of matter.
• Ions are charged atoms or groups of atoms.
• Molecules are formed when two or more atoms bond.
• Solids have particles arranged in a lattice, with limited movement.
• Liquids have weaker forces between particles, allowing for more movement.
• Gases have virtually no forces between particles; particles move freely.
• State changes (e.g., melting, freezing, evaporation, condensation) involve overcoming forces between particles.
• Elements contain only one type of atom.
• Compounds contain atoms from different elements bonded together.
• Mixtures contain different elements not bonded.
• Atoms consist of a nucleus (protons and neutrons) surrounded by electrons.
• Protons have a positive charge, electrons have a negative charge, and neutrons are neutral.
• Nucleon number (or mass number) = number of protons + number of neutrons.
• Atomic number = number of protons.
• Average atomic mass (Ar) is the weighted average of isotopes.

Chemical Changes and Physical Changes

• Chemical changes produce new substances, require energy (input or output) and are usually difficult to reverse.
• Physical changes do not produce new substances, require less energy, and are often easily reversible.
• Ions have unequal numbers of protons and electrons.
• Positive ions are called cations, negative ions are called anions.
• Ionic bonds are strong electrostatic attractions between oppositely charged ions.
• Ionic compounds form when metals lose electrons and nonmetals gain electrons.
• Covalent bonds form when nonmetals share electrons to achieve a stable outer electron configuration.
• Molecular compounds have covalent bonds, are often insoluble in water, do not conduct electricity, and can be simple or giant.
• Ionic compounds are usually soluble in water, conduct electricity when molten or dissolved, and form strong lattices.
• Elements always react in the same ratio
• Total mass never changes
• Mass of reactants = mass of products

Electrolysis

• Electricity is a stream of electrons flowing from a negative to a positive terminal.
• Only metals and graphite conduct electricity in their solid states.
• Ionic compounds only conduct electricity when molten or in solution (due to free ions).
• Electrolysis is the decomposition of ionic compounds by an electric current.
• Electrolysis separates ionic compounds into their constituent elements.
• The positive electrode (anode) is connected to the positive terminal and the negative electrode (cathode) to the negative terminal.
• Electrodes are inert materials (often carbon or platinum).
• Electroplating uses electrolysis to coat one metal with another.

Mixtures and Separating Techniques

• Solutions are mixtures of a solute dissolved in a solvent, water as common solvent for aqueous solutions.
• Solubility increases with temperature.
• Saturated solutions contain the maximum amount of dissolved solute at a given temperature.
• Separating techniques include filtration (separating solids and liquids), crystallization (separating a solid from a solution), evaporation (removing a solvent and leaving the solute behind), distillation (separating liquids with different boiling points), fractional distillation (separating liquids with close but different boiling points), and paper chromatography (separating substances based on their attraction to the solvent and the paper).
• Purity of a substance can be checked by its sharp melting and boiling point, compared to a range of temperatures with impurities.
• Impurities lower the melting point and increase the boiling point range.
• Methods to increase purity include rinsing with distilled water and repeating separation techniques.

Other Concepts

• Properties of Chlorine, Bromine and Iodine: State, color, reactivity
• Displacement Reactions: Definition
• Purity: Definition (2) and formula for purity (%) (1)
• Yield: Definition (2) and formula for yield (%) (1)
• Molecular formula: Definition (2)
• Empirical formula: Definition (1)
• Effects of low purity on melting and boiling points (2)
• Mole definition (2), symbol (1)
• Avogadro's Law (1) and molar gas volume (1)
• Common properties of elements in Group II (1) and Period 5 (1).
• Molar mass definition (1)
• Exothermic and endothermic reactions (1 each)
• Reduction and oxidation (1 each)
• Catalyst definition (1)
• Fuel cell reaction (1)
• Factors affecting reaction rate (4).
• Practical method for investigating reaction rate producing a gas.
• Explanation of temperature effect on reaction rate (3).
• Electrolysis definition (2)
• Electroplating explanation (2).
• Advantages of fuel cells compared to gasoline engines (4)
• Metallic bonding description
• Conductivity in solids in context of sodium and other metals (2)
• Structure and bonding of diamond and other related concepts

Explore the fundamental concepts of atomic structure and bonding in this quiz. Test your knowledge on atoms, ions, molecules, and the states of matter. Understand how elements and compounds interact to form the diverse materials around us.