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```B.8-B.9
In which you will learn about:
•Atomic number & mass number
•Ions
•Naming ionic compounds
8.5 The Electrical Nature of Matter
An atom consists of a
• nucleus
– (of protons and neutrons)
• electrons in space about the nucleus.
Electron cloud
Nucleus
• An atom is the smallest particle of an
element that has the chemical properties of
the element.
Copper
atoms on
silica
surface.
Distance across = 1.8 nanometer (1.8 x 10-9 m)
Subatomic Particles
• Quarks
– component of
protons &
neutrons
– 6 types
– 3 quarks =
1 proton or
1 neutron
He
ATOM
COMPOSITION
The atom is mostly
empty space
•protons and neutrons in
the nucleus.
•the number of electrons is equal to the number of
protons.
•electrons in space around the nucleus.
•extremely small. One teaspoon of water has 3
times as many atoms as the Atlantic Ocean has
teaspoons of water.
ATOMIC COMPOSITION
• Protons (p+)
–
–
–
+ electrical charge
mass = 1.672623 x 10-24 g
relative mass = 1.007 atomic mass units (amu) but
we can round to 1
• Electrons (e-)
–
–
negative electrical charge
relative mass = 0.0005 amu but we can round to 0
• Neutrons (no)
– no electrical charge
–
mass = 1.009 amu but we can round to 1
Atomic Number, Z
All atoms of the same element have
the same number of protons in the
nucleus, Z
13
Al
26.981
Atomic number
Atom symbol
AVERAGE Atomic Mass
Mass Number, A
• C atom with 6 protons and 6 neutrons is the
mass standard
• = 12 atomic mass units
• Mass Number (A)
= # protons + # neutrons
• NOT on the periodic table…(it is the AVERAGE
atomic mass on the table)
• A boron atom can have
A = 5 p + 5 n = 10 amu
A
10
Z
5
B
Atomic Symbols
 Show the name of the element, a hyphen, and the
mass number in hyphen notation
sodium-23
 Show the mass number and atomic number in
nuclear symbol form
mass number
23 Na
atomic number
11
Counting Protons, Neutrons, and
Electrons
• Protons: Atomic Number (from periodic table)
• Neutrons: Mass Number minus the number of
protons (mass number is protons and neutrons
because the mass of electrons is negligible)
• Electrons:
– If it’s an atom, the protons and electrons must be the SAME
so that it is has a net charge of zero (equal numbers of + and
-)
– If it does NOT have an equal number of electrons, it is not
an atom, it is an ION. For each negative charge, add an
extra electron. For each positive charge, subtract an
electron (Don’t add a proton!!! That changes the element!)
Learning Check – Counting
Naturally occurring carbon consists of three isotopes, 12C,
13C, and 14C. State the number of protons, neutrons, and
electrons in each of these carbon atoms.
12C
13C
14C
6
6
6
#p+ _______
_______
_______
#no _______
_______
_______
#e- _______
_______
_______
B.9 Ions and Ionic Compounds
• IONS are atoms or groups of atoms with a positive or
negative charge.
• Taking away an electron from an atom gives a CATION
with a positive charge
• Adding an electron to an atom gives an ANION with a
negative charge.
• To tell the difference between an atom and an ion, look to
see if there is a charge in the superscript! Examples: Na+
Ca+2 I- O-2 vs. Na Ca I O
Forming Cations & Anions
A CATION forms
when an atom loses
one or more
electrons.
Mg --> Mg2+ + 2 e-
An ANION forms
when an atom
gains one or more
electrons
F + e- --> F-
PREDICTING ION CHARGES
In general
• metals (Mg) lose electrons ---> cations
• nonmetals (F) gain electrons ---> anions
Learning Check – Counting
State the number of protons, neutrons, and electrons in
each of these ions.
39 K+
16O -2
41Ca +2
19
8
20
#p+ ______
______
_______
#no ______
______
_______
#e- ______
______
_______
Charges on Common Ions
-3
+1
-2
-1
+2
By losing or gaining e-, atom has same number of
e-’s as nearest Group 8A (noble gas) atom.
Forms of Chemical Bonds
Most bonds are
somewhere in
between ionic
and covalent.
• There are 3 forms bonding
atoms:
• Ionic—complete transfer of 1 or
more electrons from one atom
to another (one loses, the other
gains)
• Covalent—some valence
electrons shared between
atoms
• Metallic – holds atoms of a
metal together
Common Names
• A lot of chemicals have common
names as well as the proper IUPAC
name.
• Chemicals that should always be
named by common name and never
named by the IUPAC method are:
– H2O water, not dihydrogen
monoxide
– NH3 ammonia, not nitrogen
trihydride
COMPOUNDS
FORMED
FROM IONS
CATION +
ANION --->
COMPOUND
Na+ + Cl- --> NaCl
A neutral compound
requires
equal number of +
and - charges.
+1
Predicting Charges on Monatomic Ions
KNOW
THESE
!!!!
+2
-3
-2 -1
Cd+2
0
Properties of Ionic Compounds
Forming NaCl from Na and Cl2
• A metal atom can
transfer an electron to
a nonmetal.
• The resulting cation
and anion are
attracted to each other
by electrostatic
forces.
IONIC COMPOUNDS
NH4+
Cl-
ammonium chloride, NH4Cl
Some Ionic Compounds
Ca2+ + 2 F- --->
CaF2
Mg2+ + N-3 ---->
Mg3N2
magnesium nitride
Sn4+ + O2- ---->
SnO2
Tin (IV) oxide
calcium fluoride
Formulas of Ionic Compounds
Formulas of ionic compounds are determined from
the charges on the ions
atoms
Na  +

 F

ions
–
: F :  NaF

: 
sodium + fluorine
Charge balance:
Na+

sodium fluoride
formula
1+
= 0
1-
Monatomic Ions
Writing a Formula
Write the formula for the ionic compound that will
form between Ba2+ and Cl.
Solution:
1. Balance charge with + and – ions
2. Write the positive ion of metal first, and the
negative ion
Cl
Cl
Ba2+
3. Write the number of ions needed as
subscripts
BaCl2
Learning Check
Write the correct formula for the compounds
containing the following ions:
1. Na+, S2a) NaS
b) Na2S
c) NaS2
2. Al3+, Cla) AlCl3
b) AlCl
c) Al3Cl
3. Mg2+, N3a) MgN
b) Mg2N3 c) Mg3N2
Naming Compounds
Binary Ionic Compounds:
• 1. Cation first, then anion
• 2. Monatomic cation = name of the
element
• Ca2+ = calcium ion
• 3. Monatomic anion = root + -ide
• Cl = chloride
• CaCl2 = calcium chloride
Naming Binary Ionic Compounds

Examples:
NaCl
sodium chloride
ZnI2
zinc iodide
Al2O3
aluminum oxide
Learning Check
Complete the names of the following binary
compounds:
Na3N
sodium
________________
KBr
potassium ________________
Al2O3
aluminum ________________
MgS
_________________________
Transition Metals
Elements that can have more than one possible charge
MUST have a Roman Numeral to indicate the charge
on the individual ion.
1+ or 2+
Cu+, Cu2+
2+ or 3+
Fe2+, Fe3+
copper(I) ion iron(II) ion
copper (II) ion iron(III) ion
Names of Variable Ions
These elements REQUIRE Roman Numerals because they
can have more than one possible charge:
anything except Group 1A, 2A, Ag, Zn, Cd, and Al
(You should already know the charges on these!)
Or another way to say it is: Transition metals and the metals in groups 4A and
5A (except Ag, Zn, Cd, and Al) require a Roman Numeral.
FeCl3
CuCl
SnF4
PbCl2
Fe2S3
(Fe3+) iron (III) chloride
(Cu+ ) copper (I) chloride
(Sn4+) tin (IV) fluoride
(Pb2+) lead (II) chloride
(Fe3+) iron (III) sulfide
Examples of Older Names of Cations formed
from Transition Metals
(you do not have to memorize these)
Learning Check
Complete the names of the following binary
compounds with variable metal ions:
FeBr2
iron (_____) bromide
CuCl
copper (_____) chloride
SnO2
___(_____ ) ______________
Fe2O3
________________________
Hg2S
________________________
Polyatomic Ions
NO3nitrate ion
NO2nitrite ion
Polyatomic Ions
You can make additional polyatomic
ions by adding a H+ to the ion!
CO3 -2 is carbonate
HCO3– is hydrogen carbonate
H2PO4– is dihydrogen phosphate
HSO4– is hydrogen sulfate
Ternary Ionic Nomenclature
Writing Formulas
• Write each ion, cation first. Don’t show
charges in the final formula.
• Overall charge must equal zero.
– If charges cancel, just write symbols.
– If not, use subscripts to balance charges.
• Use parentheses to show more than one of a
particular polyatomic ion.
• Use Roman numerals indicate the ion’s charge
when needed (stock system)
Naming Ternary Compounds
 Contains at least 3 elements
 There MUST be at least one polyatomic ion
(it helps to circle the ions)
 Examples:
NaNO3
Sodium nitrate
K2SO4
Potassium sulfate
Al(HCO3)3 Aluminum bicarbonate
or
Aluminum hydrogen carbonate
Ternary Ionic Nomenclature
Sodium Sulfate
Na+ and SO4 -2
Na2SO4
Iron (III) hydroxide
Fe+3 and OHFe(OH)3
Ammonium carbonate
NH4+ and CO3 –2
(NH4)2CO3
Learning Check
1. aluminum nitrate
a) AlNO3
b) Al(NO)3
c) Al(NO3)3
2. copper(II) nitrate
a) CuNO3
b) Cu(NO3)2 c) Cu2(NO3)
3. Iron (III) hydroxide
a) FeOH
b) Fe3OH
c) Fe(OH)3
4. Tin(IV) hydroxide
a) Sn(OH)4 b) Sn(OH)2
c) Sn4(OH)
Learning Check
Match each set with the correct name:
1.
Na2CO3
a) magnesium sulfite
MgSO3
b) magnesium sulfate
MgSO4
c) sodium carbonate
2.
Ca(HCO3)2
a) calcium carbonate
CaCO3
b) calcium phosphate
Ca3(PO4)2
c) calcium bicarbonate
Mixed Practice!
Name the following:
1. Na2O
2. CaCO3
3. PbS2
4. Sn3N2
5. Cu3PO4
6. HgF2
Mixed Up… The Other Way
Write the formula:
1. Copper (II) chlorate
2. Calcium nitride
3. Aluminum carbonate
4. Potassium bromide
5. Barium fluoride
6. Cesium hydroxide
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