chem chem

• What can track changes in state of a substance?

  Heating or cooling curve
• What pattern develops in a heating curve?

  Temperature increases, then flattens out
• Why do flattening out points occur in a heating curve?

  Because a change in state is occurring
• What state change occurs at the flatline during melting?

  Solid to liquid
• What state change occurs at the flatline during evaporation?

  Liquid to gas
• Why does evaporation require more energy than melting?

  Particles are separating in a gas
• What is a limitation of the particle model?

  Not all particles are perfect spheres
• Why do atoms want a full outer shell of electrons?

  To achieve stability
• How many electrons does aluminium have?

  13 electrons
• What happens when aluminium loses three electrons?

  It has a charge of +3
• What charge does chlorine have when it gains one electron?

  -1 charge
• What is ionic bonding a result of?

  Atoms becoming ions
• How do you represent electron transfer in ionic bonding?

  Using dots and crosses
• What is the molecular formula of lithium oxide?

  Li2O
• What do ionic compounds form in a solid state?

  Giant lattices
• What is a characteristic of ionic compounds regarding melting points?

  They have high melting points
• Why do ionic compounds conduct electricity when molten or dissolved?

  Because ions are free to move
• How does the charge on ions affect boiling points?

  Higher charge leads to higher boiling points
• What is the boiling point of sodium chloride?

  Around 900 degrees C
• What is covalent bonding?

  Sharing of electrons between nonmetals
• How is the electron configuration of hydrogen represented?

  One electron in outer shell
• What happens to chlorine's outer shell during bonding with hydrogen?

  It shares an electron with hydrogen
• How does silicon tetrafluoride differ from simpler covalent compounds?

  It involves more complex bonding arrangements
• What are the key characteristics of ionic compounds?

  • High melting and boiling points
  • Conduct electricity when molten or dissolved
  • Form giant lattices
  • Strong electrostatic forces of attraction
• What are the differences between ionic and covalent bonding?

  • Ionic bonding: transfer of electrons, occurs between metals and nonmetals
  • Covalent bonding: sharing of electrons, occurs between nonmetals
• How do you determine the molecular formula from ionic charges?

  • Use the diagonal rule with charges
  • Write the formula based on the ratio of ions
• What is the electron configuration of chlorine?

  Seven electrons in its outer shell
• How can you determine chlorine's electron configuration?

  By its position in group seven
• What happens to hydrogen's outer shell when it bonds with chlorine?

  It becomes full with two electrons
• How many electrons does chlorine have in its outer shell after bonding with hydrogen?

  Eight electrons in its outer shell
• What model can be used to represent the bonding in hydrogen chloride?

  Ball-and-stick model
• What is the first step in analyzing silicon tetrafluoride?

  Check if it's a covalent compound
• What groups do silicon and fluorine belong to?

  Silicon is in group 4, fluorine in group 7
• How many bonding pairs does silicon need for a full outer shell?

  Four bonding pairs
• How many electrons does fluorine need to bond with silicon?

  One electron
• What does the little 4 in silicon tetrafluoride represent?

  Four fluorine atoms bonded to silicon
• What is the significance of the ball-and-stick model for covalent compounds?

  It visually represents the molecular structure
• What does a double bond represent in a covalent compound?

  Two lines indicating two bonding pairs
• How many electrons does oxygen usually have in its outer shell?

  Six electrons
• How do you represent double bonded covalent elements in a diagram?

  By drawing two lines between atoms