Download Day 46 - POLYTECH High School

November 1, 2012
DAY 46
AGENDA

Complete ‘Building Atoms’

Subatomic Heavyweights
MAKING SENSE
• If you know the atomic number of an element,
what other information can you figure out about
the atoms of that element?
• If you know the atomic number of an element,
can you figure out how many neutrons an atom of
that element has? Can you come up with a close
guess? Explain.
NOTES
Mass number is the number of protons plus the
number of neutrons.
 Atomic mass is the “weight” or mass of a single
atom.
 Atomic weight is the decimal number on the
periodic table.

CHECK-IN
Use your periodic table to identify the following
elements:
a) Atomic number 18
b) Has three electrons
c) Atomic mass of 16.0

WRAP-UP
Each successive element has one more proton
than the element preceding it.
 The atomic number is equal to the number of
protons.

NOTES
The number of electrons is equal to the number
of protons (as long as the atom is neutral).
 The mass number is equal to the number of
protons plus the number of neutrons (most of
the mass is found in the nucleus).

ATOMIC RESEARCH

http://app.discoveryeducation.com/search?N=
18343+4294949127&browseFilter=d_Service:
DE
Streaming,#selItemsPerPage=20&intCurrentPa
ge=0&No=0&N=18343%252B4294949125&
Ne=4294965172&Ntt=&Ns=p_wtd%257C1&N
r=&browseFilter=d_Service%253ADE%2BStrea
ming%252C&indexVersion=&Ntk=All&Ntx=mod
e%252Bmatchallpartial
LESSON 3:
SUBATOMIC HEAVYWEIGHTS
CHEMCATALYST
What is different about the two atoms?
 What is the atomic number of each atom?
 What is the mass number of each atom?
 Do you think they are both lithium atoms? Why
or why not?

THE BIG QUESTION

How do isotopes of an atom account for the
atomic weight of an element
YOU WILL BE ABLE TO:

Predict the isotopes of an element.
NOTES
Atoms of the same element that have different
numbers of neutrons are called isotopes.
 • Atomic mass units (amu) are “invented”
measurement units of the atomic mass.

MAKING SENSE

Explain why the atomic weights listed in the
periodic table are not usually whole numbers.
NOTES
While the element iron is defined as being
made up of neutral atoms with 26 protons and
26 electrons, not every iron atom has the same
number of neutrons.
 Atoms that have the same number of protons
but different numbers of neutrons are called
isotopes.

What we call the atomic weight on the periodic
table is actually the average atomic mass of
that element’s naturally occurring isotopes.
 Isotopes have similar chemical properties in
that they combine with other elements to form
similar compounds.


Atomic Weight is the weighted average of the
atomic masses of different isotopes taking into
account their abundance.
CHECK-IN

Predict the isotopes of carbon, C. Which
isotope is more abundant? How do you know?
WRAP-UP
Elements may have anywhere from 2 to 10
naturally occurring isotopes.
 The atomic weight of an element listed on the
periodic table is actually the average mass of
the naturally occurring isotopes of that
element.
 Isotopes have the same number of protons and
electrons, but different numbers of neutrons.

Isotopes of a single element exhibit similar
properties in that they form similar compounds.
 Isotopes are referred to by their mass numbers.
