Download Chapter 3, Section 1 Inside an Atom

Chapter 3, Section 1
Inside an Atom
Tuesday, November 3, 2009
Pages 76 -- 80
Objectives
Describe the structure of an atom and
define protons, neutrons, and electrons.
Explain the role of valence electrons in
forming chemical bonds.
Vocabulary Words
Nucleus
Proton
Neutron
Electron
Atomic number
Atomic mass unit
(amu)
Valence electron
Electron dot
diagram
Structure of an Atom
Atoms are extremely small.
An atom consists of a nucleus
surrounded by one or more electrons.
– The nucleus is the core of an atom.
– The nuclei contain particles called protons
and neutrons.
Protons
Protons have a
positive charge.
It is indicated by this
symbol “+”.
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Neutrons
Neutrons have no
charge.
They are neutral.
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Electrons
These particles are
energetic.
Moves in all
direction around the
nucleus.
Electrons carry a
negative charge.
It is indicated by this
symbol “-”.
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Atomic Number
Every atom of a
particular element
contains the same
number of protons.
The atomic number is
equal to the number of
protons in that element.
The atomic number is a
unique identifying
characteristic.
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Atomic Mass
Because of its size, atoms cannot be
measured with everyday units.
The atomic mass unit (amu) was
created to measure the particles in
atoms.
The majority of the atom’s mass is in
the nucleus.
Valence Electrons
Not all electrons in an atom are the same
distance from the nucleus.
Valence electrons are electrons farthest away
from the nucleus.
A chemical bond forms between 2 atoms
when valence electrons move between them.
– Valence electrons can be transferred from one
atom to another or shared between atoms.
Electron Dot Diagram
Electron Dot
Diagram is made up
of the symbol for an
element surrounded
by dots.
Each dot represents
one valence
electron.
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Homework
Workbook 3.1 (due 11/5)
Vocabulary quiz 3.1 (on 11/5)