chapter 2

• all cells share a limited number of what ingredients that combine to form different types of molecules?

  atomic ingredients
• what are biomolecules?


  molecules that are unique to living cells
• are biomolecules carbon based?

  yes
• what is matter?

  anything that has mass and occupies space
• how many different types of matter occur naturally in our universe?

  at least 92
• What is each unique type of matter called?

  element
• what is an element?


  a pure substance with distinctive chemical and physical properties
• what is the smallest unit of an element?

  atom
• what unique combinations does each type of atom contain?

  proton, electron, and neutrons
• what does the nucleus of an atom contain?

  protons and neutrons
• what are election shells?

  negatively charged electrons that move around the nucleus
• why do atoms have no electrical charge?


  it has the same number of electrons and protons
• what is an atomic number?


  represents the number of protons in an atom
• what is an atomic mass number?


  the total number of protons and neutrons in an atom
• what are isotopes?

  an element that comes in different forms and differ only in their atomic mass
• chemistry happens largely because reactive atoms interact with each other by:

  • sharing one or more electrons
  • giving up on or more electrons
  • receiving on or more electrons
• how do covalent bonds form?

  by electron sharing between atoms
• when is an atom most stable?

  when the outermost shell is filled to capacity
• how do atoms with an unfilled outermost shell achieve stability?


  by sharing electrons to fill their outermost shell to capacity, forming a molecule in the process
• what is one covalent bond?

  one pair of electrons shared between two atoms
• what are double covalent bonds?

  two pairs of electrons shared between two atoms
• what are covalent bonds?

  occur when atoms share electrons with each other to fill up their outer shells
• what are molecules?

  two or more atoms that share electrons through covalent bonds to form a chemical bond
• when is an ion formed?

  when an atom loses or gains electrons
• how does an atom become a positively charged ion ?

  when it loses one or more electrons
• how does an atom become a negatively charged ion ?

  when it gains one or more electrons
• how do ionic bonds form?

  it forms between atoms with opposite electrical charges
• what are salts held together by?

  Ionic bonds.
• what is a chemical compound?

  a substance that contains atoms from two or more different elements in a precise ratio
• what is an example of a compound?

  H2O, CO2, NaCI
• what is an example of an element?

  Oxygen (O), Hydrogen (H), Carbon (C)
• what is a chemical formula?

  it summarizes the number and type of atoms in a molecule or ionic compound
• what is the percentage of an average cell by water weight?


  70 %
• what type of molecule is water?

  polar molecule
• what is a polar molecule?

  A polar molecule is a molecule that has a positive and negative end, or a separation of electric charge, due to differences in electronegativity between its atoms.
• what is a hydrogen bond?

  the weak attraction between a hydrogen atom with a slight positive charge and a neighboring atom with a slight negative charge
• what is solution?

  A solution is a homogeneous mixture of two or more substances dissolved in fluid
• what is a solute?

  substance dissolved in fluid
• what is a solvent?

  fluid in which solute is dissolved
• why are nonpolar molecules not soluble in water?

  because water molecules cannot surround them in a hydrogen-bonded network. they are like water repellents, do not mix well with water