chem-unit 1

• What are ionic compounds formed by?


  Electrostatic attraction between positively and negatively charged ions
• What is an example of an ionic compound?


  Sodium chloride (NaCl)
• Why do ionic compounds have high melting and boiling points?


  Due to strong electrostatic forces between ions
• Why are ionic compounds solid at room temperature?


  Because strong ionic bonds hold the ions tightly in a crystal lattice
• When do ionic compounds conduct electricity?


  When molten or in aqueous solution
• Why do ionic compounds dissolve well in water?


  Due to ion-dipole interactions
• What happens to ionic compounds when they are stressed?


  They tend to shatter due to their brittleness
• Why do ionic compounds not conduct electricity in solid state?


  Because the ions are fixed in place within the crystal lattice
• What is required for electrical conductivity in ionic compounds?


  Charged particles need to be able to move freely
• What happens to ionic compounds when they are molten or dissolved in water?


  The ions become mobile and can carry an electric current
• What do ionic formulas represent?


  The ratio of ions in the compound
• How do ionic formulas help chemists?


  They help predict chemical reactions
• What can ionic formulas be used to calculate?


  The molar mass of the compound
• Why are ionic formulas essential for balancing chemical equations?


  They provide the correct ratios of ions involved in the reactions
• What does the ionic formula NaCl indicate about sodium and chloride ions?


  It contains equal numbers of sodium and chloride ions
• What does the subscript 2 in the ionic formula CaCl₂ indicate?


  The ratio of calcium to chloride ions is 1:2
• What does the subscript 3 in the ionic formula Fe₂O₃ indicate?


  There are three oxygen ions in the formula unit
• What is the charge of calcium in the ionic formula CaCl₂?


  Ca typically forms a Ca²⁺ ion
• What is the charge of chloride in the ionic formula CaCl₂?


  Cl typically forms a Cl⁻ ion
• What are the five properties of ionic compounds?


  1. High melting and boiling points
  2. Solid at room temperature
  3. Electrical conductivity when molten or in solution
  4. Solubility in water
  5. Brittleness
• What are three uses of ionic formulas?


  1. Predicting chemical reactions
  2. Calculating molar mass
  3. Balancing chemical equations
• What are the three basic components of an atom?

  Electron, proton, neutron
• What is the smallest part of an element that can exist?

  An atom
• Who proposed that all matter is made up of atoms?

  John Dalton
• What did JJ Thomson discover about atoms?

  He discovered electrons
• What did Ernest Rutherford show about atomic structure?

  The atom has a small central nucleus
• What did Neils Bohr demonstrate about electrons?

  Electrons orbit at specific distances
• What did James Chadwick discover about the nucleus?

  There are neutrons in the nucleus
• What is the charge and mass of an electron?

  Negative charge, nearly no mass
• What is the charge and mass of a proton?

  Positive charge, mass of 1
• What is the charge and mass of a neutron?

  Neutral charge, mass of 1
• Why are atoms overall neutral?

  They have equal protons and electrons
• What is the approximate size of an atom?

  0.1 nm
• How much smaller is the nucleus compared to the atom?

  About 10,000 times smaller
• What contains most of the mass in an atom?

  The nucleus
• What was the early 19th-century model of the atom called?

  Plum pudding model
• What did Rutherford's Scattering Experiment demonstrate?

  The atom has a small, positively charged nucleus
• What type of particles did Rutherford use in his experiment?

  Alpha particles
• What was the conclusion of Rutherford's experiment?

  Most particles passed through gold foil
• What is the mass number of an atom?

  Protons plus neutrons