Cheat Sheet: Atomic Foundations Of Matter

1. Introduction

1.1 Scope of chapter

• Builds on Chapter 8 - Journey Inside the Atom
• Topics: mass in physical/chemical changes; laws of chemical combination; Dalton's atomic theory; atomic combination and chemical bonds; writing chemical formulae

1.2 Key premises

2. Laws of Chemical Combination

2.1 Law of Conservation of Mass

2.2 Law of Constant Proportions (Definite Proportions)

3. Dalton's Atomic Theory

3.1 Basis and purpose

• Explains fixed mass ratios and conservation of mass by proposing atoms as indivisible particles that rearrange in reactions

3.2 Postulates of Dalton's Atomic Theory

• All matter is made of tiny particles called atoms that participate in chemical reactions
• Atoms are indivisible in chemical reactions; cannot be created or destroyed
• Atoms of a given element are identical in mass and chemical properties
• Atoms of different elements have different masses and chemical properties
• Atoms combine in simple whole-number ratios to form compounds
• Relative number and kinds of atoms are constant in a given compound

4. How Atoms Combine

4.1 Fundamental concepts

4.2 Covalent Bonding (Bonding by sharing electrons)

• Definition: bond formed by sharing of valence electrons between atoms
• Molecules of elements and compounds can form by sharing

4.3 Naming and numbering rules for covalent compounds

• First element retains its name
• Second element name ends with "-ide"
• "Mono" is usually omitted for the first element
• If prefix ends in "o" or "a" and next word starts with a vowel, drop the last vowel of the prefix
• If prefix ends in "i" and next word starts with a vowel, keep the "i"
• When hydrogen is first element, no prefix is used before it

4.4 Ionic Bonding (Bonding by electron transfer)

• Definition: electrostatic force of attraction between oppositely charged ions
• Atoms with less than 4 valence electrons tend to donate electrons
• Atoms with more than 4 valence electrons tend to gain or share electrons

4.5 Ions and ion naming

4.6 Atomic numbers and ion electron counts (selected)

4.7 Naming ionic compounds

• Cation name first, then anion name
• Simple anions end with "-ide"; polyatomic anions generally do not end with "-ide"
• Metals generally form cations; non-metals generally form anions

4.8 Polyatomic ions

4.9 Common monoatomic ions (selected)

5. Writing Chemical Formulae

5.1 Covalent compounds

• Step 1: Write symbols of constituent elements
• Step 2: Write valencies of these elements
• Step 3: Crossover valencies and write as subscripts after element symbols
• Rule: If criss-cross yields valency 1, omit the subscript

5.2 Ionic compounds

• Step 1: Write symbol of cation first, then anion
• Step 2: Write charges under the symbols (not as superscripts)
• Step 3: Criss-cross the numerical charges to obtain subscripts
• Step 4: Simplify subscripts by dividing by common factor if any
• Note: Charges on ions are not indicated in the final formula
• When a formula contains two or more of the same polyatomic ion, enclose the polyatomic ion in brackets and place the subscript outside the brackets

6. Properties: Ionic vs Covalent Compounds

• Solubility
  • Ionic: Soluble in water; insoluble in kerosene and petrol
  • Covalent: Insoluble in water; soluble in kerosene and petrol
• Electrical conductivity
  • Ionic: Do not conduct electricity in solid state; conduct in aqueous or molten state
  • Covalent: Generally do not conduct electricity even in solution
• Melting and boiling points
  • Ionic: High melting and boiling points due to strong electrostatic forces
  • Covalent: Usually have lower melting and boiling points

7. Masses of Particles and Aggregates

7.1 Molecular mass

7.2 Formula unit mass