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WHAT IS MATTER?
A BRIEF REVIEW OF THE CLASSIFICATION, PROPERTIES,
AND SEPARATION OF MATTER
MIND CATALYST
• For each image on page 19:
• Categorize the substance as either an element, a
compound, or a mixture.
• Briefly explain why you categorized it the way you did.
• Draw a particle diagram that describes your
categorization. What does an element look like on
the molecular level? What about a compound or a
mixture? Use labels if necessary.
• If the substance is undergoing a process, explain
whether it is a physical or chemical process. Justify
your answer.
MIND CATALYST
ATOMIC STRUCTURE AND
THE PERIODIC TABLE
MODERN VIEW OF ATOMIC STRUCTURE AND PERIODIC
TABLE TRENDS
A SUMMARY OF THE MODERN VIEW OF
THE ATOM
• The atom consists of positive, negative, and neutral
entities (protons, electrons, and neutrons)
• Protons and neutrons are located in the nucleus of
the atom, which is small
• Protons determine element’s identity
• There can be a variable number of neutrons for the
same number of protons – isotopes!
• Isotopes have the same number of protons but
different numbers of neutrons
• Electrons are located outside of the nucleus
• Electrons determine element’s chemical properties
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
IMPORTANT DEFINITIONS TO KNOW
• Atomic number (Z)
• Number of protons in the nucleus
• Mass number (A)
• Total number of nucleons in the nucleus (i.e., protons and
neutrons)
• Isotopes have the same Z but different A!
ISOTOPES OF CARBON
ATOMIC MASS VS. MASS NUMBER
• Look on your periodic table at the mass of carbon
• The red number is NOT the mass number!!
• It is the average atomic mass of ALL isotopes of carbon that
are known to exist
• One atomic mass unit is equal to 1.66 x 10-24 grams, which is
1/12th the mass of a 12C atom
• So, the element carbon on the periodic table is
actually a mixture of the isotopes carbon-12,
carbon-13, and carbon-14
• Therefore, the atomic mass on the periodic table is
a weighted average of the atomic mass of all
isotopes of that particular element
CALCULATING AVERAGE ATOMIC
MASS FOR AN ELEMENT
• One can calculate the average atomic weight of
an element if the abundance of each isotope for
that element is known
Average Atomic Mass
% natural abundance
=
∙ atomic mass1
100
1
% natural abundance
+
∙ atomic mass2 …
100
2
ATOMS, ELEMENTS, AND THE PERIODIC
TABLE
• The Periodic Table is used to organize the 114
elements in a meaningful way
• Arranged by increasing atomic number
THE PERIODIC TABLE
A BRIEF REVIEW OF THE ORGANIZATION OF
THE PERIODIC TABLE
• Columns in the periodic table are called groups
• Numbered from 1A to 8A or 1 to 18
• Atoms with similar properties appear in groups or families
• They are similar because they all have the same number of
valence (outer shell) electrons, which governs their chemical
behavior
• Remember, valence electrons are electrons in the highest-numbered sand p- orbitals!
• Rows in the periodic table are called periods
• Elements of the same period have the same
number of energy levels
• As you move across a period, the number of electrons and protons
increases, leading to increase in atomic number
• Elements within the same period do not generally show similarity in
properties, except d-block and f-block (lanthanides) elements
FAMILIES OF THE PERIODIC TABLE
• Some of the groups in the periodic table are
given special names, and are called families
• These names indicate the similarities of
chemical properties between group members
as a result of same number of valence
electrons:
•
•
•
•
•
Group 1:Alkali metals
Group 2: Alkaline earth metals
Group 16: Chalcogens
Group 17: Halogens
Group 18: Noble gases
A BRIEF REVIEW OF THE
ORGANIZATION OF THE PERIODIC
TABLE
• Metals are located on the left hand side of the
Periodic Table
• Most of the elements are metals
• Non-metals are located in the top right hand side of
the Periodic Table
• Elements with properties similar to both metals and
non-metals are called metalloids and are located
at the interface between the metals and nonmetals
USING THE PERIODIC TABLE TO
PREDICT ION CHARGE
• The number of electrons an atom loses or gains is
related to its position on the periodic table
• Metals tend to form cations whereas non-metals
tend to form anions
WHAT IS A CATION?
• When an atom or molecule loses electrons, it
becomes positively charged
• For example, when Na loses an electron it
becomes Na+
• Positively charged ions are called cations
WHAT IS AN ANION?
• When an atom or molecule gains electrons, it
becomes negatively charged
• For example when Cl gains an electron it
becomes Cl• Negatively charged ions are called anions
• An atom / molecule can lose or gain more than 1
electron!