Atoms And The
Periodic Table
Atomic Structure
Element – matter that is composed of one type of atom
Elements are abbreviated in scientific shorthand – either a
letter or a pair of letters called chemical symbol. Ex:
Aluminum – Al Copper – Cu
Atom – smallest piece of matter that still has the properties
of the element.
Protons – positive charge (1+)
Neutrons – neutral or no charge
Electrons – negative charge (1-)
Nucleus – located in center of atom consists of protons and
neutrons; electrons surround the nucleus
Electron Cloud – (current) model which shows electrons
travelling in specific energy levels around a nucleus;
electrons closest to nucleus have low energy, electrons
farther away have high energy.
Electrons in Energy Levels
Energy Level in Atom Energy Level in Atom
1
2
2
8
3
18
4
32
* Last energy
level can only
hold max of 8
electrons – H
and He are
exceptions
Masses of Atoms
Smaller particles of matter called quarks
exist but scientists still consider atoms to be
the basic building blocks of matter
Quark – smaller particles
that make up protons and
neutrons – six quarks are
to exist
Atomic mass – composed mostly of protons
and neutrons in the nucleus – also called
mass number
Atomic number
– the number of protons in an atom; number of
protons also identifies the element
* If you needed to find # of neutrons of an atom:
# of Neutrons = mass number – atomic number
Element from the Periodic Table
Atomic Number:
Number of protons and it is also the
number of electrons in an atom of an
element.
Element’s Symbol:
An abbreviation for the element.
Elements Name
Atomic Mass/Weight:
Number of protons + neutrons.
8
O
Oxygen
16
Components of the Atom




Protons have a mass of 1
amu (atomic mass unit).
Neutrons have a mass of
1 amu.
Electrons have very little
to almost NO mass.
The nucleus is very small
and DENSE, however, the
atom is mostly EMPTY
space
Atoms Are Neutral
◦ Atoms have no overall charge.
 This is because atoms have an EQUAL number of
protons and electrons.
 Equal number of (+) and (-) charge; they cancel
any positive or negative charges out.
Electron + Proton = Neutral
(+ ) + (-)
=0
 (A NEUTRON HAS NO CHARGE SO IT DOES NOT EVER ALTER THE
CHARGE OF THE ATOM)
• If an atom GAINS or LOSES electrons it
become a:
Negative Ion
or
Positive Ion
Isotopes
– atoms of the same element that
have different number of
neutrons.
B10 (Boron – 10) or B11 (Boron – 11)
Different isotopes have different properties.
Average atomic mass
– weighted average mass of an elements isotopes.
IONS
Ions are substances made up of
charged atoms/particles (could be
positive or negative).
 Most substances are “ionic” or have a
specific charge –
 Examples of ions:

◦ Salt, Orange Juice, Vinegar, Drain Cleaner,
Toothpaste, etc.
Common Mass Numbers
Element
BORON
CARBON
OXYGEN
SODIUM
COPPER
Symbol
Atomic
No.
Protons
Neutron
s
Mass
No.
B
5
5
6
11
10.81 amu
C
6
6
6
12
12.01 amu
O
8
8
8
16
16 amu
Na
11
11
12
23
22.99 amu
Cu
29
29
34
63
63.55 amu
Nitty Gritty Science, LLC ©2016
Ave. Atomic
Mass
The Periodic Table
Periodic Table – Table where elements are
organized by increasing atomic number
(number of protons).
Dmitri Mendeleev (1800s) – created first
periodic table based on atomic mass.
Henry Moseley
arranged elements
by atomic number
(what we use today.)
- The periodic table is arranged by groups
and periods
Groups – Vertical columns of elements
with similar properties - groups are
numbered 1-18
.
Elements in the
Same GROUP are
most chemically
similar / have
similar properties.
-
Elements in the same group have same
number of valence electrons in their outer
energy level (“1’s” place)
- EXCEPT TRANSITION
METALS (ENTIRE MIDDLE SECTION
Groups # 3-12)
* These elements have different numbers
of valence electrons and do not follow
the same rules as the rest of the table.
Ex: Group 13 has 3 valence electrons,
group 18 has 8, etc.
Periods
– Horizontal ROWS of elements. Periods are
numbered 1-7
Elements in the same period have the same
number of energy shells / orbitals in
common.
Ex: H & He are in 1st pd – they both have 1
energy shell.
Metals
– Good conductors of heat and electricity, ALL but
mercury are SOLID at room temperature
* Metals are located on the left side of the period
table. Pd table is mostly Metals.
Metalloids – Elements that make up stair step;
have properties of both metals and non-metals.
Nonmetals
– Elements that are usually GASES or brittle solids
at room temperature; located on the right of the
table.
Electron Dot Diagram
– Uses the element symbol and dots to
represent outer energy level electrons only
(valence). Use pd table to assist you in
creating these. (Groups)
- Begin dots at the top and continue in the
clockwise direction. MAXIMUM of 8
VALENCE E’s.
He
O
Ne
Al
Metals
– good conductor of heat and electricity, all but mercury are
solid at room temperature
* Metals are located to the left of stair step
Alkali Metals
– (Group 1) are the most reactive of all metals; don’t occur
in nature in their element form
Alkaline Earth Metals
– (Group 2) shiny, ductile and malleable; combine readily
with other elements
Transition Elements
– (Group 3 – 12) most familiar metals because they often
occur in nature uncombined
Inner Transition Metals – (listed below table)
 Lanthanide Series – elements with atomic # 58 – 71
 Actinide Series – elements with atomic # 90 –103
Nonmetals
– elements that are usually gases or brittle solids at room
temperature; most can form ionic and covalent compounds
– located to the right of the stair step.
Noble gases – (Group 18) exist as isolated atoms. They are all stable
because outer energy level is filled
Metalloids – elements that make up stair step; have me have metallic and
non-metallic properties
Metalloids are part of the mixed groups – which contain metals, nonmetals and metalloids (mixed groups are Group 13, 14, 15, 16, 17)