Bio Chapter 2

Distinguish between an element and a compound.

• An element can be made of multiple types of atoms; a compound is a single type of element.
• An element is substance that cannot be broken down into other substances by ordinary chemical procedures whereas a
  compound is made of two or more elements in fixed ratio

• An element is a single type of atom; a compound is a combination of two or more different elements.
• An element is a type of molecule; a compound is a single atom.

Identify the four elements that make up 96% of living matter

• sodium, chlorine, iodine, selenium
• iron, magnesium, zinc, copper
• sulfur, phosphorus, calcium, potassium
• carbon, hydrogen, oxygen, nitrogen

Trace elements are essential, but needed in only minute amounts (Ex. Fe, I)

• Trace elements are harmful in large amounts.
• Trace elements are essential nutrients needed in minute amounts.
• Trace elements are only found in animal products.
• Trace elements are not necessary for human health.

Describe the structure of an atom --> Define and distinguish among atomic number, mass number, atomic weight,
and valence

• The nucleus of each atom has a characteristic number of protons, which are positively charged, and neutrons,
  which are electrically neutral

• Atomic number: Each atom of a particular element has the same unique number of protons

• Mass number
  : The number of particles in the nucleus-- protons plus neutrons

• Isotopes: Elements whose atoms vary in neutron number and mass number (remember that the proton number
  DOES NOT change, just the number of neutrons). An isotope may or may not be radioactive

Given the atomic number and mass number of an atom know how to determine the number of its neutrons,
number of electrons.

• Neutrons = Atomic Number + Mass Number; Electrons = Mass Number
• Neutrons = Atomic Number; Electrons = Mass Number - Atomic Number
• Neutrons = Mass Number; Electrons = Mass Number - Atomic Number
• Neutrons = Mass Number - Atomic Number; Electrons = Atomic Number

Explain how its electron configuration influences the chemical behavior of an atom.

• The number of electrons in an atom’s outer shell are it’s valence electrons and largely determine it’s chemical
  properties. The chemical properties of an atom depend mostly on the number of electrons in its outermost electron
  shell.

• An atom is most stable when it has a full outermost shell-- two electrons for small atoms such as hydrogen and eight
  electrons for larger atoms such as carbon or chlorine

• By transferring or sharing electrons, atoms complete their outer shells. These interactions between atoms create
  chemical bonds. Atoms which need to give up or acquire only one or two electrons to complete their valence shells
  are the most chemically reactive (EX. Na+1 , Cl-1).

Define: Covalent Bonds

• Covalent bonds are formed by the transfer of electrons between atoms.
• Covalent bonds are weak attractions between molecules.
• Covalent bonds occur only in ionic compounds.
• Covalent bonds are chemical bonds formed by the sharing of electron pairs between atoms.

Define: Nonpolar Covalent Bonds

• Nonpolar covalent bonds are chemical bonds where two atoms share a pair of electrons equally.
• Nonpolar covalent bonds are characterized by the formation of ionic compounds.
• Nonpolar covalent bonds are formed when atoms have a large difference in electronegativity.
• Nonpolar covalent bonds involve the transfer of electrons between atoms.

Define: Polar Covalent Bonds

• Polar covalent bonds are chemical bonds where electrons are shared unequally between two atoms, leading to partial charges.
• Polar covalent bonds do not create any partial charges on the atoms involved.
• Polar covalent bonds involve the complete transfer of electrons between atoms.
• Polar covalent bonds are formed only between identical atoms.

Define: Molecule

• A molecule is a single atom.
• A molecule is a type of chemical reaction.
• A molecule is a mixture of different substances.
• A molecule is a group of two or more atoms held together by covalent bonds.