CH 115 Fall 2014
Worksheet 6
1. What does it mean for a set of atoms/ions to be isoelectronic? Can you give an
example of 4 species that are all isoelectronic with each other?
If atoms/ions are isoelectronic with each other, that means that they have the
same number of electrons or the same electron configuration. Ex. Mg2+, Na1+,
Ne, F1-, O2-, N32. Define ionization energy. What is the periodic trend involving ionization energy?
Ionization energy is the amount of energy that is needed to take an electron
away from an atom. As you go down a group on the periodic table, ionization
energy decreases due to increasing atomic radii and less effective nuclear
charge. As you go across a period, ionization energy increases due to more
valence electrons and smaller atoms which hold electrons in tighter.
3. Define electron affinity. What is the periodic trend involving electron affinity?
Electron affinity is the amount of energy that is released when an atom
absorbs or adds an electron. THESE ARE NEGATIVE NUMBERS – the more
negative the electron affinity, the easier this process is. There is no trend
going down a group. Across a period, electron affinity is more positive
(harder) for atoms that already have a full shell of electrons.
4. Distinguish between a molecular compound and an ionic compound.
A molecular compound is one that forms through the sharing of electrons
between two nonmetals. An ionic compound is one that forms between a
metal and a nonmetal (no sharing of electrons  one takes and one gives).
5. List a couple of rules for naming binary molecular compounds (those with two
different elements).
Name the first element as it is found on the periodic table. Name the second
element, adding an “ide” suffix to the stem of the element name. Use Greek
prefixes to indicate the number of atoms of each element that are present
(caveat – if there is only one atom of the first element present, you do not need
to add the prefix “mono”).
6. Name or give the formula for each of the following.
a). SiO4
silicon tetroxide
b). dichlorine heptoxide
Cl2O7
c). I2
elemental iodine – NOT a binary molecular compound
d). trinitrogen tetroxide
N3O4