Transcript Unit 4 power point notes

Unit 4 Periodic Table and
Chemical Change

Introduction to
the Atom
Structure of an Atom

A carbon atom consists of protons
and neutrons in a nucleus that is
surrounded by electrons.
Isotopes


Isotopes are atoms with same
number of protons but different
number of neutrons.
Examples are C-12 and C-14
Isotopes
Chapter 3
section 2
Organizing Elements


Rows tell us the
number of levels of
electron an
element has.
Rows are called
Periods



Elements in
columns have
similar properties
and reactivity
Columns are called
Groups or
Families
Group # tells # of
electrons in outer
level
Finding Data on Elements

Each square of the periodic table
includes an element’s atomic
number, chemical symbol, name,
and atomic mass.
Chapter 3
section 2

Organizing the
Periodic Table
The Three Major Categories of
Elements



Metals
Nonmetals
Metalloids
Metals




elements that are shiny
good conductors of thermal energy
and electric current
Malleable (they can be hammered
into thin sheets of metal) and
ductile (they can be drawn into thin
wires)
Nonmetals



elements that
are dull (not
shiny)
poor conductors
of thermal
energy and
electric current.
Solid nonmetals
– brittle and
unmalleable
Metalloids
Metalloids


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
or semiconductors, elements that
have properties of both metals and
nonmetals
Some can be shiny or dull,
some can be malleable and ductile
some can conduct thermal energy
and electric current well.


Most reactive elements are group 1
& 2 on the left side of Periodic Table
Elements decrease in reactivity as
they move to the right on Periodic
Table.
Forces on Atoms




Gravity – gravitational attraction
Electromagnetic Force – particles with
same charge repel, opposite charges
attract
Strong Force – force that keeps protons in
the nucleus from repelling
Weak Force – effects the unstable atoms,
can cause a neutron to change into a
proton and an electron
2 types of Chemical Bonds

Ionic Bonds – an unequal sharing of
electrons


NaCl, H2O
Covalent Bonds – equal sharing of
electrons

O2, Cl2
Chemical Equation

Law of Conservation of Mass –
states that matter cannot be
created or destroyed
Chemical Changes


Chemical change – combustion,
electrolysis, oxidation and
tarnishing
Signs that chemical change has
occurred:

Odor, light, heat or sound production,
foaming or fizzing and change in color