Transcript Ionic Compounds

Ionic
Compounds
Ion Review
Ion:
an atom that has gained or
lost an electron.
We write an ions as follows: Cl- or
Na+
Ions behave differently from the
neutral element.
Cation
Cations:
ions with a positive
charge.
They have more protons than
electrons.
Anions
Anions:
negatively charged ions.
They have more electrons than
protons.
Electron = e-
Noble Gases
Elements
want to be like the noble
gases.
Every element wants to be stable,
thus they want to have a full octet
of electrons like the noble gases.
FULL OCTET
Noble
gases are stable with
a full octet. (octet rule)
Their s and p configurations
are full.
s and p have a total of 8
electrons.
Octet: a group of eight.
Ne = [He]2s22p6
Ionic Compounds
 Ionic
Compound is any chemical
compound composed of oppositely
charged ions.
 In order to attract, the ions want to create a
neutral charge (all the negatives are
balanced by the positive)
 Al3+O2- is aluminum oxide.
 Questions: How would we balance out
these charges to be neutral (charge is 0)?
READING IONIC COMPOUNDS
Al2O3
In
the example above, the
number to the bottom right
tells you how many of each
ion you have.
 The
2 says you have 2 Al+3 ions
 The 3 says you have 3 O-2 ions
TRY SOME OF THESE
+
1. Na
-2
O
+
+2
2. Ba + Cl
+3
-2
3. Fe + O
Ionic Compounds
An
ionic compound composed of
a simple cation and simple anion.
For instance NaCl is a binary ionic
compound (has just 2 ions).
Na+ + Cl- → NaCl (the charges
cancel out)
Losing an electron
NOTICE
In
the previous slide,
Na now has a full
octet
Gaining an electron
REACHING A FULL OCTET
When
the Na+ lost an
electron and the Cl- gained
an electron, both ions
resemble the stable NOBLE
GAS
What holds salt
together?
All
salts are held together by ionic
bonding.
The attraction is so strong that many
sodium and chloride ions are pulled
together into a tightly packed
structure.
What holds salt
together?
All
salts are held together by ionic
bonds.
Halogens that are ions are called
halides
 All the simple anions formed
from group 7.
F-, Cl-, Br-, I-, At-
Energy
Ionization
energy is the energy
that must be supplied to remove
the outermost electron from an
atom.
Atoms always resist having their
electrons removed.
Energy
 What
do you think takes more
energy to remove an e Li
 Br
 HINT: Draw the shorthand electron
configuration. Which ion would be
the closest to a noble gas
ANSWER
 Li
 [He]2s1
 Br
 [Ar]4s23d104p5
 If
you remove 1 e- from Li, you form the
noble gas He
 If you remove 1 e- from Br, you don’t
form any noble gas
 Li is more energetically favorable to lose
an e-
GENERAL TRENDS
 As
you move from left to right on
the periodic table, the ionization
energy increases
 As you go down the periodic table
(the quantum number increases),
the ionization energy decreases
 The electrons are further from the
nucleus and not as strongly
attracted
GENERAL TREND
 As
a result of ionization energies,
you can predict atomic size:
 As
you move from left to right, e- are
more attracted to the nucleus
 THIS MEANS ATOMIC SIZE DECREASES
FROM LEFT TO RIGHT
 As you move down the periodic table,
e- are less attracted to the nucleus
 THIS MEANS ATOMIC SIZE INCREASES AS
YOU GO DOWN THE PERIODIC TABLE
SUMMARY POINT
Ionization
energy and atomic
size are opposite
As the ionization energy
increases, the atomic size
decreases
As the ionization energy
decreases, the atomic size
increases
Monatomic Ion
Monatomic
ion: a simple ion
formed from a single atom.
Example: CaBr2 (charges
balance)
 Made from Ca+2 and Br-
Polyatomic Ion
Polyatomic
ion: a charged group of
two or more bonded atoms that
functions as a single ion.
Most polyatomic ions consist of atoms
of several elements.
Example: K2CO3 (charges balance)
 Made from K+ and CO3-2
ION SHEET
The
following handout gives
you a lot of information on ions
Name of the ion
Symbol for the ion
Charge associated with the
ion
HOW DO YOU CREATE COMPOUNDS
WITH POLYATOMIC IONS?
The
formation of a compound
with polyatomic ions is just like
regular ionic compounds
YOU JUST HAVE TO BALANCE OUT
THE CHARGE
EXAMPLE
 Let’s
create the compound with the
following ions:
 Ba+2 and CN To balance out the charges we need:
 1 Ba+2, and
 2 CN Since the CN- is two elements, we have
to put a parenthesis around it
 Ba(CN)2
TRY THESE
Na+,
SO4-2
Fe+3,
C2O4-2
+
NH4 ,
-2
CO3
SUMMARY OF STEPS
1.
2.
3.
Balance out the charges between
each ion.
Write down the metal (or the
polyatomic ion with the + charge)
first
Write the number of the ion to the
bottom write of the symbol (if it is a
polyatomic ion, you must put the
entire ion in brackets if there is more
than 1)
SUMMARY OF STEPS
4.
5.
Write out the symbol for the
second ion (either the nonmetal
or the negatively charged
polyatomic ion)
Write the number of the ion to the
bottom write of the symbol (if it is a
polyatomic ion, you must put the
entire ion in brackets if there is
more than 1)