Chapter 8: Elements and Chemical
Bonds
Subtitle
Lesson 1: Electrons and Energy Levels
• The Periodic Table
• Organizes the chemical elements
• Each block describes basic properties of one
element
• List elements is order by atomic number
• Elements in each group have similar chemical
properties
The Periodic Table (continued)
• Metals are on the left side of the periodic
table.
• Nonmetals are on the right side of the
table.
• Metalloids are located in a narrow stairstep region between metal and nonmetals
Atoms Bond
• 1. Most of the matter around you is made up of
compounds that include two or more different elements
• 2. A chemical bond is a force that holds atoms together
• 3. Atoms contain protons with a positive charge, neutrons
with a neutral charge, and electrons with a negative
charge.
Atoms Bond
3. Atoms contain protons with a positive charge, neutrons with a neutral
charge, and electrons wit a negative charge
• a. Electrons are the atomic particles that participate in chemical bonding.
• b. The amount of energy an electron can have is an energy level.
• c. Electrons closest to the nucleus have the least energy; electrons
farthest fro the nucleus have the most energy.
• d. The maximum number of electrons in the first energy level, which is
closest to the nucleus, is two. The maximum number of electrons in the
second energy level is eight.
• e. The outermost electrons in an atom are involved in chemical bonding.
These electrons are less strongly attached to the nucleus.
Atoms Bond
• 4. A valence electron is an outermost electron.
• a. The number of valence electrons in an atom tells
you how many bonds an atom can form.
• b. Each element in the same group in the periodic
table has the same number of valence electrons.
Atoms Bond
• 5. The electron dot diagram is a model that represents
valence electrons in an atom as dots around the element’s
chemical symbol.
• a. To create an electron dot diagram, draw one dot for each
electron in the atom, placing one dot on each of the four
sides of the symbol and then pairing additional dots.
• b. The number of unpaired dots in an electron dot diagram
tells you how many bonds an atom can form.
Atoms Bond
• 6. Many atoms are stable with eight electrons. An atom with at least
one unpaired electron is unstable.
• a. Stable atoms do not easily react with or form bonds with other
atoms.
• b. Group 18 includes the noble gases; with the exception of helium,
each of these gases have eight valence electrons and are stable.
• c. unstable atoms can become stable only by forming chemical
bonds with other atoms.
• d. atoms tend to gain, lose, or share valence electrons until each
atom has the same number of valence electrons as the noble gases.
• e. stable atoms have four pairs of valence electrons
Lesson 2: Compounds, Chemical Formulas, and
Covalent Bonds
• From Elements to Compounds
• 1. Compounds are chemical combinations of two or
more elements.
• 2. Compounds and the elements that form them
often have different chemical and physical properties.
• 3. Atoms can bond to form compounds by sharing
valence electrons.
From Elements to Compounds
• 4. A chemical formula is a group of chemical symbols
and numbers that represent the elements and the
numbers of atoms of each element in a compound.
• 5. The letters in a chemical formula represent
elements.
• 6. Molecular models show the shape and
appearance of the arrangement of atoms in a
compound
Covalent Bonds – Electron Sharing
• 1. A covalent bond is a chemical bond formed when
two or more atoms share one or more pairs of
valence electrons.
• 2. When forming water, valence electrons are shared
between oxygen and hydrogen atoms, thereby
forming a covalent bond to make three stable atoms.
Covalent Compounds
• 1. a molecule is group of atoms held together by
covalent bonding that acts as an independent unit.
• 2. Covalent compounds generally have low melting
points and low boiling points. They are poor
conductors of electricity.
• a. In a hydrogen molecule, a single covalent bond
forms when each atoms shares its valence
electrons with the other.
Covalent Compounds
• b. In a carbon dioxide molecule, a double covalent
bond forms when the carbon atom shares two pairs
of valence electrons with each oxygen atom.
• c. In a triple covalent bond, three pairs of valence
electrons are shared between two atoms.
• d. Triple covalent bonds are stronger than double
covalent bonds, which are stronger than single
covalent bonds
Covalent Compounds
• 3. In a covalent bond, one atom can attract the shared
electrons more strongly than the other atom can.
• a. In a molecule of water, the oxygen atom attracts the
electrons more strongly than each hydrogen atom does.
b. Because the electrons have slight negative charge,
there is a slight negative charge near the oxygen atom;
there is a slight positive charge near the hydrogen
atoms.
Covalent Compounds
• 3c. A molecule that has a slight positive end and a
slight negative end because of unequal sharing of
electrons is a polar molecule.
• 3d. Polar molecules, such as sugar and water,
dissolve easily in one another because of the
attraction of opposite charges.
• 4. Molecules made up of atoms of the same
element are nonpolar because the atoms are
identical. So they share electrons equally.
Ionic Bonds
• 1. When a metal and a nonmetal bond, they do not
share electrons.
• 2. The metal atom transfers on or more valence
electrons to the nonmetal atom, forming a chemically
stable compound.
• 3. an ion is an atom that is no longer electrically
neutral because it has lost or gained one or more
valence electrons.
Ionic Bonds
• 3a. An atom that loses one or more valence electron
becomes an ion with a positive charge.
• 3b. An atom that gains one or more valence
electrons becomes an ion with a negative charge.
• 4. Sodium is a metal that has one valence electron.
• 4a. To become stable, sodium has to lose a
valence electron. So, when a sodium atom loses a
valence electron it becomes a positively charged
ion.
Ionic Bonds – Electron Transferring
• 1. When forming a chemical bond, the nonmetal
atoms gain the electrons lost by the metal atoms.
• 2. Due to the change in the number of electrons, the
metal and nonmetal atoms both become ions.
• 3. The attraction between positively and negatively
charged ions in anionic compound is an ionic bond.
Ionic Compounds
• 1. Most ionic compounds are solid and brittle at room
temperature.
• a. Ionic compounds usually have high melting points
and boiling points.
• b. Ionic compounds are good conductors of electricity
because electric charge passes easily from one ion to
another.