ch 4 l 3 how atoms differ
TRANSCRIPT
Chapter 4: Understanding the AtomLesson 3: Elements, Isotopes and Ions – How Atoms DifferMs. Dewey-Hoffman, 2011
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QTT: 4-6 Sentences!!!
How do elements differ?
What do you think isotopes are?
What do you think ions are?
How can atoms interact?
Is it easy or hard to make elements interact?
SCAN
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Vocabulary
Periodic Table: Chart that lists elements by atomic number and by electron arrangement
Average Atomic Mass: Total mass of an atom
Element: Pure substance made from atoms that all have the same number of protons
Atomic Number: Number of protons in an atom of an element
Ion: Atom that has gained or lost electrons and is no longer neutral
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Vocabulary
Mass Number: Sum of the number of protons and neutrons that an atom has
Isotopes: Atoms of the same element that have different numbers of neutrons
Contrast: To show differences when compared
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Different Elements – Different Number of Protons
An ELEMENT is a pure substance made from atoms that all have the same number of protons.
All atoms of the same element have the same number of protons.
The number of protons in the atom of an element is the element’s ATOMIC NUMBER.
PROTONS ARE THE ONE CONSTANT THING IN THE ATOM. This is why we organize elements by their proton number.
All Aluminum atoms have 13
protons.
Therefore, all atoms with 13 protons
are Aluminum
atoms. Aluminum’s
atomic number is 13.
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Finding the Atomic NumberAtomic Number on the Periodic Table for Each Element
Find the element.
Look near the top of it’s box.
It’s the WHOLE number.
Found on page 195
A Periodic Table is a chart that lists elements by atomic number
and by electron arrangement.
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The Periodic Table: Other Information
Elements in the periodic table are arranged horizontally in order of increasing atomic numbers.
The elements are also arranged vertically in groups with similar chemical properties.
Most tables provide each element’s name, atomic number, symbol and atomic mass (in AMU).
Name
Symbol
Atomic Mass
Atomic Number
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The Periodic Table
Found on Page 196
METALLOID = SEMIMETAL
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Isotopes-Different Numbers of Neutrons
Atoms of the same element always have the same number of protons.
HOWEVER, atoms of the same element sometimes have different numbers of neutrons. ISOTOPES
ATOMIC NUMBER = Number of Protons
An atom’s MASS NUMBER is the sum of the number of protons and neutrons the atom has.
How to Determine an Atom’s Number of Neutrons
# of Neutrons = Mass Number – Atomic Number
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Isotopes of Neon (Just the Nucleuses)
10 Neutrons
10 Protons
12 Neutrons
10 Protons
Net Charge of Atom is Still Neutral
Pages 197-198
Contrast = To Show Differences When Compared
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Isotopes
Atoms of the same element that contain different number numbers of neutrons are called ISOTOPES.
Because most elements have more than one isotope, each element has an AVERAGE ATOMIC MASS.
The AVERAGE ATOMIC MASS of an element is the weight average mass of the mixture of an element’s isotope.
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Isotopes and Radioactivity
Radioactive isotopes have unstable nuclei that break down and release particles, radiation, and energy.
Its not good for you, but it is useful.
Carbon-14 is useful for dating bones, wood and charcoal up to 50,000 years old.
Uranium-238 is used by geologists to determine the age of rocks.
Californium-252 is used to inspect airline luggage for hidden explosives and weapons.
More on page 199 of your textbook.
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Isotopes of HydrogenRegular
Hydrogen
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Positive Ions – Losing Electrons
When an atom loses an electron, it has more protons than electrons positive charge.
An atom that has a positive net charge is called a POSITIVE ION.
Positive ions are represented with the element symbol and a super script: H+, Ca2+
Elements on left Give up electrons.
Positive
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Negative Ions – Gaining Electrons
When an atom gains an electron, it has more electrons than protons negative charge.
An atom that has a negative net charge is called a NEGATIVE ION.
Negative ions are represented with the element symbol and a super script: Fl-,O 2-
Elements on right Take electrons.
Negative
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Opposites Attract!
Positive and Negative Ions attract each other because of their opposite charges.
This is how COMPOUNDS are formed.
Example: Sodium Chloride (table salt).
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In Class AssignmentEnrichment & Reinforcement.
HomeworkPage 202: 1-8 all.
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Mini Quiz
Clear your desks (all you need is a pencil or a pen).
For the element ____________, which has an atomic number of _______ and an atomic mass of ___________.
Draw an atom of this element that has NO NET CHARGE. With the correct number of protons and neutrons on the nucleus area and electrons at the correct energy levels.
On the back, draw the same element as an ion with a charge of ______ one.
Use + to represent protons, - for electrons and 0 for neutrons.