Good to know chem

• How many hydrogen atoms are in H₂O?

  2 hydrogen atoms
• Why does H₂O have 2 hydrogen atoms and 1 oxygen atom?

  Atoms need electrons to be stable
• What is the octet rule?

  Atoms want full outer shells of electrons
• What are the valence electrons and stability needs for Hydrogen and Oxygen?

  • Hydrogen (H): 1 valence electron, needs 1 more (wants 2 total)
  • Oxygen (O): 6 valence electrons, needs 2 more (wants 8 total)
• How many bonds does one oxygen atom form in H₂O?

  2 bonds
• How many bonds do the two hydrogen atoms form in H₂O?

  Each forms 1 bond
• What type of compound is H₂O?

  Covalent compound
• Why do atoms form compounds?

  To gain, lose, or share electrons for stability
• What is the formula for magnesium chloride?

  MgCl₂
• Why does magnesium become Mg²⁺?

  It loses 2 valence electrons
• Why do chlorine atoms become Cl⁻?

  They gain 1 electron
• How many chlorine atoms are needed to balance one magnesium atom?

  2 chlorine atoms
• Why isn’t oxygen just O?

  Single O atoms are very reactive
• What is the natural form of oxygen?

  O₂ (two O atoms double-bonded)
• What are the 7 diatomic elements?

  H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂
• What is a mnemonic for the 7 diatomic elements?

  "Have No Fear Of Ice Cold Beer"
• Why do diatomic elements pair up?

  They need few electrons to be stable
• What are the summary rules for atomic bonding?

  • Atoms bond to achieve a full outer shell
  • Number of atoms depends on electrons gained/lost/shared
  • Subscripts reflect how many atoms are needed for stability
  • Diatomic elements pair up when alone due to instability
• What is a compound?

  A substance made of chemically bonded elements
• How is a compound represented?

  By a chemical formula
• Can compounds be separated physically?

  No, only by chemical means
• What is a mixture?

  A physical combination of substances
• How can mixtures be separated?

  By physical methods
• What are the differences between compounds and mixtures?

  Compound:

  • Has a chemical formula
  • Chemically bonded
  • Fixed ratio of components
  • Cannot be separated physically
  • New properties form

  
  

  Mixture:

  • No single formula
  • Not chemically bonded
  • Ratios can vary
  • Can be separated physically
  • Original properties remain