ATOMS, ELEMENTS, MOLECULES
COMPOUNDS AND NOMENCLATURE
Outline
Element and Atom
Atomic Number and Atomic Mass Number
Ions, Molecules and Compounds
Objectives:
Be able to:
i. Differentiate between the subatomic particles of an
atom:
• Protons
• Neutrons and
• Electrons
ii. To explain the structure of the nucleus.
iii. To identify the atomic number and Atomic Mass
Number
iv. Identify various atoms and Elements of the Periodic
table
v. Explain –ve and +ve charges on ionic species of Atoms
vi. Name Ions, molecule and compounds
An atom is …
• Atoms are the basic building
blocks of matter.
EVERYTHING on Earth is made of atoms…
even the air and Your Body!
Drugs
Water
Carbonated Beverages etc..
Atoms are made of three particles:
• Protons (+)
e• Neutrons (N)
e-
• Electrons (e-)
+ N+
N+
+N
e-
Electron
Proton
Neutron
Protons
• Located in the nucleus
• Have a positive charge
• Have a mass of one
Neutrons
• Located in the nucleus
• Have no charge
• Have a mass of one
–similar to the proton
eN
e-
Electrons
•
•
•
•
Have a negative charge
Orbit the nucleus of the atom
Are very small (have basically NO mass)
In a neutral atom, there are the same number of protons and
Structure of An Atom
Neutron
-
Electron
+
Proton
+
-
What force holds all the
parts of an atom together?
• It is the electromagnetic force of attraction
between the positive protons in the nucleus
and the negative electrons orbiting around
the nucleus that holds the atom together.





Lets take a look deep inside
ATOM = Proton(s) + Neutron(s) + Electron(s)
This is an Electron.
- charge
eNo Mass
+
N
This is a Neutron.
No Charge
Mass of ONE
This is a Proton.
+ Charge
Mass of ONE
Identifies the
atom
Atomic Number
Is the number of PROTONS in the atoms of an element.
• It is an IDENTITY of elements on the Periodic Table.
• All known elements can be found on the periodic table.
• Elements can be identified by their atomic number.
• It can be used like a social NRC number for people.
Example:
An element with 8 protons has an atomic number of 8 and is
the element Oxygen from the Periodic Table.
Problem Set-1: Class Examples
• Identify the element and tell how many protons
it has:
1) Atomic number 7
Nitrogen: 7 protons
2) Atomic Number 20
Calcium: 20 protons
• Identify the element and give its atomic number.
3) 15 protons
4) 4 protons
Phosphorus: Atomic number 15
Beryllium: Atomic Number 4
• Give the atomic number and number of protons.
5) Argon
Atomic number 18; 18 protons
6) Sulfur
Atomic number 16; 16 protons
Atomic Mass Number
• Is the total number of Protons and Neutrons
of the atom of an element.
• Protons and Neutrons are the two largest
particles in the atom.
• Since they are both located in the nucleus,
the mass of the atom is located in the
nucleus.
Atomic Mass Number = Protons + Neutrons
The Periodic Table
Atomic Number
- Gives number of protons
- identifies the element
7
N
Element Symbol
Gives the name of
the element.
14
Atomic Mass Number
-The number of protons + neutrons.
Commonly, Atomic Mass Numbers are decimal fractions because
of Isotopic effects.
Isotopes
Are atoms of the same element with Same Proton Number But
different Neutron Number.
6
6
C
C
12
C-12 (98.9%)
6
13
C-13 (1.10%)
C
14
C-14 (1ppt)
Relative Atomic Mass = m1x1 + m1x1 + m1x1
Relative Atomic Mass = 12x0.989 + 13x0.01 + 14x10-09
Relative Atomic Mass = 12.01 amu
Problem Set-2: Class Examples
Give the name of the Element, its Atomic Number, Number of Protons,
and Atomic Mass Number.
Beryllium
Atomic number 4
4 protons
Atomic mass number 9
Sodium
Atomic number 11
11 protons
Atomic mass number 23
Oxygen
Atomic number 8
8 protons
Atomic Mass Number 16
Compounds contain more than one type of atom!
Example 1:
Organic Compound (a compound with carbon and hydrogen atoms):
 Methane (natural gas) – CH4
1 atom of carbon and
4 atoms of hydrogen)
Example 2:
Inorganic compound (a compound without carbon and hydrogen atoms):
 Water – H2O
 2 atoms of hydrogen and
1 atom of oxygen)
+
K
Cl
An ion is an atom or group of atoms with a positive or negative
charge!!
 A particle with a neutral charge has the same number of
protons and electrons.
 An ion does not have the same number of electrons and protons.
 Examples of ions:
• H+ - A hydrogen atom that is missing one electron.
The atom has one more proton than electron,
and must have a positive charge.
•CO32- - Carbonate has two more electrons than protons
Cl
+
K
Cations and Anions
 A particle with a positive charge Mn+. Is called a Cation: e.g Fe2+
 A particle with a positive charge Xn-. Is called a Anion: e.g H Examples of ions:
• H+ - A hydrogen atom that is missing one electron.
The atom has one more proton than electron,
and must have a positive charge.
•CO32- - Carbonate has two more electrons than protons
MOLECULES AND COMPOUNDS
(NOMENCLATURE)
• The inorganic chemical nomenclature
was devised by the International Union
of Pure and Applied Chemistry (IUPAC).
• Precisely identify the chemical
composition of the compound.
• Based on the Law of Constant Composition
 Proportions of lements in a compound
are ALWAYS the same!
Naming Rules For Monoatomic Ion
RULES FOR Mn+ : M = Metal, n = oxidation number
• If element forms only one cation, we name it by its element
name:
 Na+ = sodium ion
 Al3+ = aluminum ion
• If a transition metal can form more than one cation, add ion’s
charge in Roman numerals to the name.
 Fe2+ is iron(II) ion (ferrous)
 Fe3+ is iron(III) ion (Ferric).
Some Elemental Formulae and Their Ions
No.:
Element
Symbol
Ion (s)
Name of Ion
1
Sodium
Na
Na+
Sodium ion
2
Potassium
K
K+
Potassium ion
3
Calcium
Ca
Ca2+
Calcium ion
4
Aluminium
Al
Al3+
5
Zinc
Zn
Zn2+
6
Copper
Cu
Cu+, Cu2+
Cu(I), Cu(II)
7
Iron
Fe
Fe2+, Fe3+
Fe(I), Fe(II)
8
Lead
Pb
Pb2+, Pb4+
Pb(II), Cu(IV)
• Name the ion by its element name
• For variable cations of the same element, add ion’s charge in
Roman numerals to the name.
 Fe2+ is iron(II) ion (ferrous)
 Fe3+ is iron(III) ion (Ferric).
Ion Names: Classical System
Element
Formula
Lower Charge
Name
Formula
Higher
ChargeName
Copper
Cu+
cuprous
Cu2+
Cupric
Iron
Fe2+
ferrous
Fe3+
ferric
Lead
Pb2+
plumbous Pb4+
plumbic
Mercury
Hg2+
2
mercurous Hg2+
mercuric
Tin
Sn2+
stannous
Sn4+
stannic
This is for information and for homework only; classical names will
not be on quiz or test unless part of a common name that’s required.
Some Elemental Formulae and Their Ions
No.:
Element
Symbol
Ion (s)
Name of Ion
1
Hydrogen
H2
H-
Hydride ion
2
Nitrogen
N2
N3−
Nitride ion
3
Oxygen
O2
O2-
Oxide ion
4
Fluorine
F2
F-
Fluoride ion
5
Chlorine
Cl2
Cl-
Chloride ion
6
Bromine
Br2
Br -
7
Iodine
I2
I-
• Take the root of the element name
• Add the suffix “-ide” at the end of the name:
Common and Systematic Names
No.:
Common Name
Chemical Formula
SYTEMATIC NAME
1
Laughing gas
N2O
Dinitrogen Monoxide
2
Ammonia
NH3
Ammonia
3
Table salt
NaCl
Sodium Chloride
4
Baking soda
NaHCO3
Sodium Hydrogen Carbonate
5
Borax
Na2B4O7●10H2O
Sodium tetraborate decahydrate
6
Hypo
Na2S2O3
Sodium Thiosulphate
7
Acetylene
C2H2
Ethyne
8
Wood Alcohol
CH3OH
Methanol
9
Grain alcohol
CH3CH2OH
Ethanol
10
Vinegar
CH3COOH
Acetic/ Ethanoic Acid
Naming Rules For Monoatomic Ion
RULES Xn- IONS:
• Take the root of the element name
• Add the suffix “-ide” at the end of the name:
 Cl- = chloride ion
 Se2- = selenide ion
 N3- = nitride ion
 Most often ions are formed when metals combine with
nonmetals. (Exception is NH4+ with anion.)
THE CHARGE ON AN ION CAN BE PREDICTED FROM
ITS POSITION IN THE PERIODIC TABLE
elements of Group IA
have a +1 charge
elements of
Group VA have a
-3 charge
elements of
Group IIA have a
+2 charge
elements of
Group VIA have a
-2 charge
elements of
Group VIIA have a
-1 charge
NAMING IONIC COMPOUNDS
RULES
i.
Always put cation before anion in formula
ii.
Name of compound is just cation name followed by anion
name.
EXAMPLES:
CATION
ANION
Ma+
Xb-
Ma+b
Xb-a
Ma+bXb-a
MbXa
 If a = b, then both = 1 by definition for lowest ratio
NAMING IONIC COMPOUNDS
RULES
i.
Always put cation before anion in formula
ii.
Name of compound is just cation name followed by anion
name.
EXAMPLES:
No.:
Cation
Anion
Compound
Name of Compound
1
Mg2+
F-
MgF2
magnesium fluoride
2
Fe2+
Br-
FeBr2
iron(II) bromide
3
Fe3+
Br-
FeBr3
iron(III) bromide
4
Ag+
CO32-
Ag2CO3
Silver carbonate
5
Ma+
Nb-
Ma+bNb-a
PROBLEM SET-1: Class Example
Write the formula of barium phosphide
Step 1. Write down the formulas of the ions.
Ba2+
P3Step 2. Combine the smallest numbers of Ba2+ and P3- so that
the sum of the charges
3(Ba2+) + 2(P3-) = 0
3(2+) + 2(3-) = 0
The correct formula is Ba3P2
PROBLEM SET-1.2: Class Example
1.2.1 Figure out the charge on each x:
a) ZnX,
b) NH4X,
c) (NH4)2X,
d) Al2X3,
e) X2(SO3)3
Example 1.2.2: From the about list of compound,
identify and write down:
a) Compounds where X is cation
b) Compounds where X is anion
Naming Compounds Containing Polyatomic Ions
• A polyatomic ion is an ion that contains two or more elements.
E.g
NO-3
• Compounds containing polyatomic ions are composed of
three or more elements.
E.g Na 2CO 3
• They usually consist of one or more cations combined
with a negative polyatomic ion.
• When naming a compound containing a polyatomic ion,
name the cation first and then name the anion.
This is the way the
formula is written.
Na 2CO3
2Na
+
23
CO
The ions are what is
actually present.
ANIONS WITH HYDROGEN
Some anions have picked up one or two hydrogen ions.
Old naming rules put “bi” in front of the anion name.
IUPAC uses hydrogen or dihydrogen:
CO32- with one H+ added is HCO3Carbonate ion becomes hydrogen carbonate ion.
Name these:
i. PO43-,
ii. HPO42-,
iii. H2PO4-
One group of ionic compounds that contains all nonmetals is the
ammonium salts. Try to write formulas for ammonium sulfate and
ammonium phosphate.
Four polyatomic ions that do not use the –ate/ ite
system.
OH
-
-
HS
Hydroxide
Hydrogen Sulfide
CN
O
-
Cyanide
22
Peroxide
Binary compounds contain only two different elements.
There are four main types, listed in following slides.
A. Binary Ionic Compounds Containing a Metal Forming
Only One Type of Cation (salts) e.g. Na2O; ZnCl; AlCl3
B. Binary Ionic Compounds Containing a Metal
That Can Form Two or More Types of Cations (still
salts): FeCl2; FeCl3; CuCl; CuCl2
C. Binary Compounds Containing Two Nonmetals (Binary
Covalent) Compounds between nonmetals are
molecular, not ionic. N2O; N2O4, H2O
D. Acids Derived from Binary Compounds: HCl, HBr, HI
A. Binary Ionic Compounds Containing a Metal Forming
Only One Type of Cation (salts) e.g. Na2O; ZnCl; AlCl3
 Is a metal combined with a non-metal.
 Name the metal followed by the root name of the
nonmetal stem plus the suffix –ide.
 Here the number of atoms of each element present is not
expressed in the name.
 Practice: CaC2, MgBr2, Al2O3, NaH (calcium carbide,
magnesium bromide, aluminum oxide, sodium hydride)
B. Binary Ionic Compounds Containing a Metal
That Can Form Two or More Types of Cations (still salts)
 Name the metal
 Charge in Roman numerals,
 Name the nonmetal which has stem plus the suffix –ide.
 Here, the number of atoms of each element present is not
expressed in the name.
Practice:
–
–
–
–
FeS:
iron (II) sulfide
CuCl;
Copper (I) chloride
SnF2,
tin(II) fluoride
Mn3(PO4)5: manganese (V) phosphate
C. Binary Compounds Containing Two Nonmetals
(Binary Covalent) Compounds between nonmetals are
molecular, not ionic.
– The element that more electropositive (least electronegative) is
named first.
Rules:
 Give Greek prefix (to indicate number of atoms of first
element)
• Don’t use mono prefix for first element. (NO2)
 Give Greek prefix (to indicate number of atoms of second
element) to root of element name, then add -ide
Example: N2O3 is dinitrogen trioxide.
Exception: hydrogen never has prefix.
Some Greek Prefixes
S No.
Number
Greek Prefix
A
1
mono
B
2
di
C
3
Tri
D
4
Tetra
E
5
penta
F
6
hexa
G
7
hepta
H
8
octa
I
9
nona
J
10
deca
Binary Compounds
S No.
COMPOUND
NAME
A
N2O3
Dinitrogen trioxide
B
PCl5
Phosphorous pentachloride (not mono-)
C
Cl2O7
-------
D
CCl4
E
CO
Carbon tetrachloride
Carbon monoxide
F
CO2
Carbon dioxide
G
PI3
--------
H
H2S
Hydrogen sulfide (hydrogen never gets a prefix)
I
H2O
------
J
HCl
k
----
phosphorous trichloride
l
----
dichlorine oxide
D. Acids Derived from Binary Compounds
• Certain binary hydrogen compounds, when
dissolved in water, form solutions that have acid
properties.
• The aqueous solutions of these compounds are
given acid names.
• The acids names are in addition to their –ide
names.
• Hydrogen is typically the first element of a binary
acid formula.
D. Acids Derived from Binary Compounds
• To name binary acids write the symbol of
hydrogen first.
• After hydrogen write the symbol of the second
element.
• Place the prefix hydro- in front of the stem of the
nonmetal name.
• Place the suffix -ic after the stem of the nonmetal
name. Practice: HCl, H2S, HI (hydrochloric acid,
hydrosulfuric acid, hydroiodic acid)
A.
B.
C
.
D
.
If an ionic compound is a hydrate, it will have
•H2O in the formula, like MgCO3•6 H2O
 Name the ionic compound part using ionic naming rules,
 Give the Greek prefix for the number of water molecules
 Add the word hydrate:
hexa
MgCO3•6H2O
Hydrate
Magnesium carbonate
NOTE: Numbers and corresponding Greek prefixes
FORMULA
# H2O
GREEK
PREFIX
CLASSICAL
NAME
SYSTEMATIC
NAME
1
CaSO4*2 H2O
2
di
gypsum
Calcium sulfate
dihydrate
2
MgSO4*7 H2O
7
hepta
epsom salts
Magnesium sulfate
heptahydrate
3
Na2CO3*10
H2O
10
deca
washing soda
Sodium carbonate
decahydrate
4
CuSO4*5 H2O
5
penta
bluestone
Copper(II) sulfate
pentahydrate
At this level, no naming rules at all
Just learn formulas and names.
CH4
methane
C3H8
propane
C8H18
octane
CH3OH
methanol
CH3CH2OH
ethanol
CH3CHOHCH3 Propanol
COOH
Formic acid
CH3COOH
acetic acid
C6H12O6
glucose
CH3NH2
aminomethane
C12H22O11
sucrose
C2H2
ethyne