Compound

• What are substances formed from two or more elements called?

  Compounds
• How are the atoms in a compound arranged?


  The atoms are in fixed proportions throughout the compound and held together by chemical bonds.
• What is involved in making chemical bonds?


  Atoms give away, take, or share electrons.
• What is required to separate the original elements of a compound?

  A chemical reaction
• What happens to metal and non-metal atoms during ionic bonding?


  Metal atoms lose electrons to form positive ions, while non-metal atoms gain electrons to form negative ions.
• What is ionic bonding?


  It is the strong attraction between positively and negatively charged ions.
• Give an example of a compound that is bonded ionically.


  Sodium chloride
• How do compounds formed from non-metals differ from those formed from metals?


  Compounds formed from non-metals consist of molecules, while those formed from metals consist of ions.
• What is covalent bonding?


  It is when each atom shares an electron with another atom.
• Provide an example of a compound that is bonded covalently.


  Water
• How do the properties of a compound compare to the properties of its original elements?


  The properties of a compound are usually totally different from the properties of the original elements.
• What happens when iron and sulfur react to form iron sulfide?


  The compound formed is a dull grey solid lump that behaves differently than either iron or sulfur.
• How can compounds be represented?


  By formulas made up of element symbols.
• What does the formula CO₂ represent?


  It represents a compound formed from 1 carbon atom and 2 oxygen atoms.
• What is the formula for sulfuric acid?


  H₂SO₄
• What does a small number outside brackets in a formula indicate?


  It applies to everything inside the brackets.
• What is the formula for calcium hydroxide?


  Ca(OH)₂
• What are some examples of common chemical formulas?


  1. Carbon dioxide – CO₂
  2. Ammonia – NH₃
  3. Water – H₂O
  4. Sodium chloride – NaCl
  5. Carbon monoxide – CO
  6. Hydrochloric acid – HCl
  7. Calcium chloride – CaCl₂
  8. Sodium carbonate – Na₂CO₃
  9. Sulfuric acid – H₂SO₄
• How many atoms are in one particle of Na₂CO₃?


  6 atoms
• What is the smallest particle of an element?

  Atom
• What surrounds the nucleus of an atom?


  Electrons
• What is a molecule?


  A particle that consists of two or more atoms chemically bonded together
• How is an element defined?


  A substance made of only one type of atom that can't be broken down
• What is a compound?


  A substance made of two or more elements chemically combined
• How is a compound formed?

  By chemical reactions
• Give an example of a compound.

  HCl
• What is a mixture?


  A mixture contains two or more substances not chemically combined together
• Provide an example of a mixture.

  Air
• What are isotopes?


  Forms of an element that have the same number of protons but different numbers of neutrons
• How is relative atomic mass calculated?


  By adding up all the masses of isotopes in an element
• If an element has isotopes with masses of 10 and 11, and abundances of 20% and 80% respectively, what is the relative atomic mass?


  $10.8$
• What is the formula for calculating relative atomic mass using isotopes?


  $X =$ \frac{(10 \times 20) + (11 \times 80)}{100}