Lecture 31 Ion Formation Ozgur Unal 1 Slide 2 Calcium carbonate
CaCO3 2 Table salt NaCl Aluminum oxide Al2O3 Slide 3 The elements
in the same group show similar chemical properties. The chemical
properties are determined by the valence electrons. These valence
electrons are involved in the formation of chemical bonds between
two atoms. A chemical bond is the force that holds two atoms
together. Two types of chemical bonds: Ionic bond and Covalent
bond. 3 Ionic bonds form by attraction between positive ions and
negative ions. Slide 4 A short review: Electron-dot structure shows
the number of valence electrons of elements. Check out Table 7.1
Ionization energy increases from left to right across a period.
Noble gases (except He) have 8 valence electrons and they have very
high ionization energies chemically stable. The octet rule states
that atoms tend to gain, lose or share electrons in order to
acquire a full set of 8 valence electrons. 4 Slide 5 A positive ion
forms when an atoms loses one or more valence electrons in order to
attain a noble gas configuration. A positively charged ion is
called a cation. Example: Na 1s 2 2s 2 2p 6 3s 1 Ne 1s 2 2s 2 2p 6
Sodium has one valence electrons. According to the octet rule, Na
loses its valence electron to have the same electron configuration
with Ne. Therefore, Na forms a sodium cation Na + Note that, Na +
is still a sodium atom with different chemical properties. Na +
still has 11 protons. It is not a Neon atom! 5 Slide 6 6 Example:
Show the electron configuration of Ca and write its electron dot
structure. Which noble gas configuration does Ca attain according
to the octet rule? Metal Ions: Metal ions are reactive because they
lose valence electrons easily. The group 1 and 2 metals are most
reactive metals on the periodic table. Some group 13 atoms also
form ions. Check out Table 7.2 Slide 7 Transition Metal Ions: In
general, transition metals have an outer energy level of ns 2. They
also fill their d orbitals. These metals commonly lose their two
valence electrons from s orbital forming +2 cations. However, they
also commonly lose their d electrons forming +3 cations or greater.
Example: Iron, Fe, can form both +2 or +3 ions. Copper, Cu, forms
both +2 and +3 ions. 7 Slide 8 Pseudo-noble gas configuration:
According to the octet rule, elements reach chemical stability when
they have the electron configuration of noble gases. However, there
are other stable electron configurations. For example, elements in
groups 11-14 lose electrons to form an outer energy level
containing full s, p and d sublevels. Example: Z 1s 2 2s 2 2p 6 3s
2 3p 6 4s 2 3d 10 Zinc atom loses 2 electrons in the 4s orbital. Z
+2 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 is called pseudo-noble gas
configuration. 8 Slide 9 9 Nonmetals easily gain electrons to
attain a stable outer electron configuration. Example: Cl 1s 2 2s 2
2p 6 3s 2 3p 5 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 Cl - 1s 2 2s 2 2p 6 3s 2
3p 6 An anion is a negatively charged ion. Cl - is an anion. Check
out Figure 7.4 To designate an anion, the ending ide is added to
the root name of the element. Cl - is called choride. How is the
anion of Nitrogen called? Slide 10 Example: Show the electron
configuration and electron-dot structure of Oxygen atom. Also show
the electron configuration of oxide. 10 Activity: Show the
electron-dot structure, electron configuration of each element
below. What type of ion(s) do these elements form? State the charge
of each ion. I Ca Cu P Rb - Cu Ba C Fe Cl Ra Fe
