Download Chapter 3 Section 2 Notes

Unit 5 Section 2 Notes
A Guided Tour of the Periodic
Table
Who is Dmitri Mendeleev? (1834-1907)

In 1869, Dmitri Ivanovitch Mendeléev
created the first accepted version of the
periodic table.
What is the Periodic Table?
Shows all known elements in the universe
 Organizes elements by chemical
properties

The Periodic Table

The periodic table groups similar elements
together. This organization makes it
easier to predict the properties of an
element based on where it is in the
periodic table.
Elements

Elements in the periodic table are
represented by their symbols.



The first letter is ALWAYS capital
If there is a second letter, it is ALWAYS
lowercase
Every element has its own unique symbol
Cu
C
Carbon
Copper
How is the Periodic Table Organized?
The elements are arranged based on the
number of protons in the nucleus.
 Periodic Law: states that when elements
are arranged in order of increasing atomic
number, similarities in their properties will
occur in a regular pattern.

Periods in the Periodic Table




Period: a horizontal row of elements in the
periodic table
As you move from left to right in a period, the
number of protons and electrons increases by
one
Elements in the same period DO NOT have
similar properties; in fact, they change greatly
across the row
The first element in a period is always an
extremely active solid. The last element in a
period, is always an inactive gas.
Groups or Families in the Periodic
Table
Group or family: a vertical column of
elements in the periodic table
 All elements in a family have the same
number of valence electrons, so they
have similar properties



For example, lithium (Li), sodium (Na),
potassium (K), and other members of group 1
are all soft, white, shiny metals.
These elements are NOT exactly alike because
they have different numbers of protons
Ions
Ionization: the process of adding electrons
to or removing electrons from an atom
 Ion: an atom that has lost or gained one
or more electrons and has a net electric
charge
 Cation: an ion with a positive charge
 Anion: an ion with a negative charge

Goal of Atoms

All atoms want to have a FULL octet (8 ein outer shell)

They do this by gaining, losing, or sharing
electrons
Metals and Electrons
Metals LOSE electrons to form cations
 Example: Lithium loses one electron to
become a lithium ion, written as Li+

p+
Second energy
level can hold
up to 8 e-. It is
easier to lose 1
e- than gain 7
more.
3 electrons
After lithium
loses an
electron, it has
a full
outermost
energy level.
3
4 n0
3 p+
4 n0
2 electrons
Nonmetals and Electrons
Nonmetals GAIN electrons to form anions
 Example: Fluorine gains one electron to
become a fluoride ion, written as F
9 p+
10 n0
9 electrons
Second energy
level can hold
up to 8 e-. It is
easier to gain 1
e- than lose 7
more.
After fluorine
gains an
electron, it has
a full
outermost
energy level.
9 p+
10 n0
10 electrons
So, how do compounds form?
So, how do compounds form?
So, how do compounds form?
Atomic Number
Atomic Number: how many protons are in
the nucleus of an atom
 Remember that ATOMS are neutral, so
they have equal numbers of protons and
electrons


Therefore, atomic number also tells the
number of electrons for atoms only
Mass Number (Atomic Mass)

Mass Number: the number of protons and
neutrons in an atom


Mass number is ONLY protons and neutrons
because they provide most of an atoms mass
The same element can have different
mass numbers because they may have
different numbers of neutrons.
Isotopes

Isotopes: atoms of the same element
having the same number of protons but
different numbers of neutrons

Each “version” of the atom has the same
number of protons and electrons
Isotopes
Some isotopes are more common than
others
 For example, protium is found most often

Calculating Neutrons in an atom

To calculate the number of neutrons in an
atom, take mass number minus atomic
number.
Mass Number
- Atomic Number
# of Neutrons
Average Atomic Mass
In the periodic table, the atomic mass is a
decimal because it is an average of all the
naturally occurring isotopes
 When calculating neutrons from average
atomic mass, round to the nearest whole
number
 Example: How many neutrons are in Zinc?
(Atomic Number 30; Average atomic mass
65.39)


65-30 = 35 neutrons
How do you read the Periodic Table?
Periodic Table Song

http://www.youtube.com/watch?v=zUDDi
WtFtEM