Introduction to Atoms ions isotpesHTRHRYU.ppt

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1. Introduction to Atoms, Ions
and Isotopes
Honors Coordinated Science II
Wheatley-Heckman

2. What are atoms?
•The atom is a basic unit of
matter that consists of a
dense, central nucleus
surrounded by a cloud of
negatively charged electrons.
•While all atoms have protons,
neutrons and electrons, atoms
of different elements have
different numbers of these.

3. Atoms
•Each element on the periodic table has
an atomic number, which tells how many
protons an atom of that element has.
•Each element also has an mass number.
•Mass number = # of Protons + # of Neutrons

4. Electrons
•Neutral atoms have the same number of
electrons (negative charge) as they do
protons (positive charge).
•# of electrons = atomic number
•ONLY IN NEUTRAL ATOMS

5. Let’s Practice!
•Find Boron on the periodic table.
•How many protons does an atom of Boron
have?
•How many neutrons?
–Hint: If the mass number is a decimal, round it
to the nearest whole number to calculate # of
neutrons.
•How many electrons?

6. Ions
•An atom or small molecule with an
overall positive or negative charge due
to an imbalance of protons and
electrons.
–# of protons does not change
–# of electrons changes.
–Positive charge = loss of electrons
–Negative charge = gain of electron

7. Ions Continued…
•Ions are represented by a superscript
charge on the element symbol.
–Examples: F
-
, Mg
2+
, Al
3+
Practice:
•How many protons, neutrons, and
electrons does Al
3+
have?

8. Isotopes
•All neutral atoms of the same element
have the same number of protons, and
therefore the same number of
electrons.
•The number of neutrons CAN vary.
•Isotopes: atoms of an elements that
have the same number of protons, but
a different number of neutrons.

10. Average Atomic Mass
•The mass shown on your periodic table
as a decimal is the average atomic
mass.
–Average mass of all isotopes of an atom in
nature.

11. Example: Lithium
•2 Isotopes are found in nature:
Lithium-6 and Lithium-7 (Lithium-8 is
radioactive and quickly decays)
•Atomic mass is listed as 6.94.
•How is that possible?
–94% of Li atoms have an atomic mass of 7,
and 6% have an atomic mass of 6.
–Avg. Atomic Mass = (7 x .94) + (6 x .06)

12. Let’s Review!
•________ are charged atoms.
–_________ ions have LOST electrons.
–_________ ions have GAINED electrons.
•An atom of Cu
2+
has:
–________ protons
–________ neutrons
–________ electrons

13. More Review
•____________ are atoms of the same
element that have different numbers of
neutrons in the nucleus.
•What does average atomic mass
represent?