6.2 & 6.3 Molecules Key Concepts How are atoms held together in a covalent bond? What happens when atoms don’t share electrons equally? What factors determine whether a molecule is polar? How do attractions between polar molecules compare to attractions between nonpolar molecules?

Recall that ionic bonds form between _______________ charged ions Which ion is the metal cation? Which ion is the nonmetal anion? Can two nonmetals form an ionic bond? oppositely Sodium (Na+) Chloride (Cl-) No, their charges will repel

Covalent Bonds Two or more nonmetals, like two chlorine atoms, will ________________ electrons instead of transferring them By sharing, the atoms remain ______________ and do _______ become ions…so they won’t repel share neutral not

How many valence electrons does each chlorine atom have? Cl Cl Where can two chlorine atoms share electrons to make a bond? 7 (Group 7A) Between the unpaired valence electrons

_______________ than ionic bonds Covalent Bonds A chemical bond in which two atoms share a pair of valence electrons is called a ______________ bond. covalent The attractions between the shared electrons and each ___________ is enough to hold the atoms together _______________ than ionic bonds nucleus Weaker

There are several ways to show a covalent bond. Covalent Bonds There are several ways to show a covalent bond. A pair of dots is replaced by a _______ line Show the orbitals that ___________ overlap

Molecules of Elements A neutral group of atoms that are joined together by one or more covalent bonds is called a _________________ A chemical formula can also be used to describe the molecule…for example, a molecule of hydrogen is represented with the formula ________. molecule H2

Many nonmetal elements exist as diatomic molecules. Covalent Bonds Many nonmetal elements exist as diatomic molecules. Diatomic means “_______ __________” two atoms

“7 Up”…start with nitrogen, which has atomic number _____ Make a “7” and go “Up” to ___________ 7 hydrogen

Multiple Covalent Bonds The hydrogen atoms share ______ pair of electrons…which is a called a ___________ bond It is also possible for atoms to fill their outer energy levels by… sharing ______ pairs of electrons, called a _______________ bond one single two double 3 N N triple

Nitrogen for example, is in Group 5A…so put 5 valence electrons around each nitrogen atom N N Each nitrogen needs _____ more valence electrons to meet the octet rule, so it will form three bonds 3

To name molecular compounds, simply… write out the name of the first _________ follow it by the name of the second nonmetal with its ending changed to _____. Add a ___________ to the name of each element to indicate _______ _________ atoms of element are present nonmetal -ide prefix how many

The name for the molecule N2O3 is… ____________ Example: The name for the molecule N2O3 is… ____________ # of atoms prefix dinitrogen trioxide

Special Prefix Rules If only one atom of the _________ element is listed, the prefix _________ is ___________ Example: the name for NO2 is… ______________ Instead of mononitrogen dioxide first mono- omitted nitrogen dioxide

Example: the name for NO is… _____________ Also, if the vowel combinations _____ or _____ appear next to each other in a name, the _______ vowel is omitted Example: the name for NO is… _____________ instead of nitrogen monooxide o-o a-o first nitrogen monoxide

Practice! Name the following molecules… S2Cl2 _____________ SO3 _____________ N2O5 _____________ CO2 _____________ CO _____________ disulfur dichloride sulfur trioxide dinitrogen pentoxide carbon dioxide carbon monoxide

More Practice! Write formulas for the following molecules… Silicon dioxide _______ Iodine heptafluoride ______ Dinitrogen monoxide _____ carbon tetrachloride ______ SiO2 IF7 N2O CCl4

What best describes a covalent bond? Assessment Questions What best describes a covalent bond? An attraction between ions with opposite charges The sharing of protons between neutral atoms The sharing of electrons between neutral atoms The sharing of neutrons between ions

Which “seven” nonmetals are diatomic? Assessment Questions Which “seven” nonmetals are diatomic? N2 O2 F2 Cl2 Br2 I2 H2

3. Name the following molecular compound…IF7 Assessment Questions 3. Name the following molecular compound…IF7 Iodine heptafluoride