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## Unit 5 Section 2 Notes

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### Title: Chapter 3 Section 2 Notes Author: alovallo Last modified by: Ashley LoVallo Created Date: 10/28/2009 1:37:47 PM Document presentation format – PowerPoint PPT presentation

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Title: Unit 5 Section 2 Notes

1
Unit 5 Section 2 Notes
• A Guided Tour of the Periodic Table

2
Who is Dmitri Mendeleev? (1834-1907)
• In 1869, Dmitri Ivanovitch Mendeléev created the
first accepted version of the periodic table.

3
What is the Periodic Table?
• Shows all known elements in the universe
• Organizes elements by chemical properties

4
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.

5
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
6
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.

7
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.

8
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9
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

10
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11
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

12
Goal of Atoms
• All atoms want to have a FULL octet (8 e- in
outer shell)
• They do this by gaining, losing, or sharing
electrons

13
Metals and Electrons
• Metals LOSE electrons to form cations
• Example Lithium loses one electron to become a
lithium ion, written as Li

Second energy level can hold up to 8 e-. It is
easier to lose 1 e- than gain 7 more.
After lithium loses an electron, it has a full
outermost energy level.
2 electrons
3 electrons
14
Nonmetals and Electrons
• Nonmetals GAIN electrons to form anions
• Example Fluorine gains one electron to become a
fluoride ion, written as F-

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 electrons
10 electrons
15
So, how do compounds form?
16
So, how do compounds form?
17
So, how do compounds form?
18
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

19
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.

20
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

21
Isotopes
• Some isotopes are more common than others
• For example, protium is found most often

22
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
23
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

24
How do you read the Periodic Table?
25
Periodic Table Song