Download Chocolate Challenge - Waterford Public Schools

Chocolate Challenge
Find the 12 differences between the two pictures.
Source: http://www.smart-kit.com/wp-content/uploads/2008/03/chocolate-puzzle.jpg
The answers are …
Source: http://www.smart-kit.com/wp-content/uploads/2008/03/chocolate-puzzle.jpg
Atoms and
Their Structure
Timeline of Development of Current
Atomic Model
Discovery Discovery
of the
Neutron
of the
Proton
450 BC
Democritus
proposed
the idea of
atomos
1802
Beginning
of
Modern
Atomic
Theory
1897
1911 1913 1930
Discovery
of the
Nucleus
Discovery
of the
Electron
Introduction
of the wave
mechanical
model
The Idea
of Energy
Levels for
Electrons
was
Proposed
What is Today’s Atomic
Model?
Dense, Positively
Charged
Nucleus
Mostly
Empty
Space
Composed of Protons,
Neutrons, and Electrons
Negatively
Charged
Electron Cloud
Most Probable
Location of the
Electrons
A Summary of Atomic
Structure

The atom consists of positive, negative, and neutral entities called
protons, electrons, and neutrons



Protons determine element’s identity
 # of protons is unique for each element
Electrons determine element’s chemical properties
Neutrons act as a “glue” for the protons to minimize charge repulsions

Protons and neutrons are located in the nucleus of the atom, which is
small
 Therefore, the nucleus is positively-charged

Electrons are located outside of the nucleus at an average distance
of 10-8 cm
 Therefore, the electron cloud is negatively-charged
Nucleus Size vs. Electron Cloud Size
• Most of the
volume of the
atom is due to
electrons
Masses of the Proton, Neutron,
Electron
• Most of the mass of the atom is due to the
protons and neutrons within the nucleus
Nucleus Size vs. Electron Cloud
Size
Element Symbols, Atomic Number,
and Mass Number

Atomic number (Z)


Represents the number of protons in the nucleus
Mass number (A)


Represents the total number of nucleons in the nucleus (i.e.,
protons and neutrons)
Mass Number = # of protons + # of neutrons
Mass number is NOT the number on the Periodic Table

Although numerically similar, this is the average atomic mass –
more on this later!
Isotopes
 There
can be a variable number of
neutrons for the same number of protons
 Isotopes have the same number of
protons but different numbers of neutrons

“Different” versions of the same element
 Masses
are different due to the different
number of neutrons

So, isotopes have the same Z but different
A!
Isotopes of Carbon
An Element’s Charge
 All
elements on the periodic table are
electrically neutral

 In
Positive charge of the protons equals
negative charge of the electrons
order for an element to be neutral, the
number of protons must equal the number
of electrons
 Atomic number equals number of
electrons!
Calculating # of Protons,
Electrons, and Neutrons
Atomic #
Na
Hg
Mass #
# of P+
# of N
# of E-
Isotopic Forensics