- The document discusses atoms and the periodic table. It provides information on the structure of atoms including electrons, protons, and neutrons. - Key points from the periodic table are that elements are organized on it and each has an atomic symbol. The periodic table can provide atomic mass and other information about elements. - Atoms consist of electrons in an electron cloud surrounding the nucleus of protons and neutrons. Protons have a positive charge while electrons have a negative charge, making the overall atom neutral. Isotopes are variants of elements with different numbers of neutrons.

1. Agenda Bell work
• Notes: Atoms on the
• What is the Periodic Table
Periodic Table
and organization of?
• History of the Atom• What type of information
can be found on the periodic
HW: Chp 17 pg 291-299 table?
Review Q’s 1-20

2. Atoms on the Periodic
Table
March 13, 2013

3. Objectives
1. Describe the present model of the
atom explaining electrons, neutrons,
and protons

4. Periodic Table
Atoms make up all matter
Elements are any material that is made up
of only one type of atom
Elements are organized onto the periodic
table

5. Each element is designated an atomic
symbol on the periodic table

6. Atoms
Atoms cannot be
seen with visible light
Robert Brown
First to discover direct
evidence of the atom

7. An Atom is made up of three parts:

Protons
 Neutrons
 Electrons

8. Electrons
Electrons surround the nucleus in an
electron cloud
Electrons carry a negative charge
The atom is mostly empty space

9. Electron Cloud Model

10. Why don’t we pass through one another?
Electrical repulsion – two electrons with
negative charges will repel each other

11. Protons
Protons and neutrons are bound to the
atomic nucleus
Protons carry a positive charge
Protons are identified by Atomic number
atom is electrically neutral: Number of
protons = number of electrons;

12. Neutrons
Neutron has no electrical charge, but the
same mass as a proton
Protons and neutrons are called nucleons
Mass given to each proton and neutron is 1

13. Atomic Mass
• Electrons are so small they are
considered negligible in mass
• Atomic mass is measured in the unit –
amu
 Atomic Mass Unit
Atomic mass on the periodic table

14. Mass Number, Isotopes and
Ions
December 18, 2012

15. Electrons are so small they are
considered negligible in mass
Protons and neutrons in the nucleus
• Atomic mass is measured in the unit –
amu
 Atomic Mass Unit

16. Atomic Mass
Atomic mass on the periodic table –
average of all its isotopes
Isotope – an Element with differing
number of neutrons

17. Mass Number
Mass number = total number of protons
and neutrons
Identify isotopes by the mass number

18. Writing Isotopic Symbols
X = element symbol
A = Mass Number
Z = Atomic Number
Total number of neutrons:
 Mass Number – Atomic number = number of
neutrons

19. Isotopic Notation
Hydrogen - 2, has one proton and one
neutron
Hydrogen - 3, has one proton and two
neutrons

20. Ions
Atoms that gain or lose electrons
Lose electrons – positive in charge
Gain electrons – negative in charge

21. Hydrogen that has lost an electron
H+1
Hydrogen that has gained an electron
H-1