Download Ions + Isotopes

Comparison of Atomic Models
Learning Target
•
•
Know the differences between electrons,
protons, and neutrons.
Determine the number of electrons and protons
in a neutral atom and ion.
Relative Size
Electrons
Charge: Negative (-)
Mass: Near Zero
Protons (positive)
Charge: Positive (+)
Mass: About 2000x Larger than electron
Neutrons (neutral)
Charge: Neutral
Mass: Comparable to proton
A Little More About Charge
A Coulomb (C) is an amount just like “a dozen” is
an amount.
1C = 6.24x1018 the charge of electrons
The reason for this definition is because electrons
are so small that we need to account for A LOT of
them (1018) to be able to describe a charge on the
macroscopic scale.
Comparison of Subatomic Particles
Charge(C)
Mass (g)
1.602 x 10-19
1.67x10-24 1.0073=
1
Neutron Inside
nucleus
0
1.68x10-24 1.0087=
1
Electron Outside
nucleus
-1.602 x 10-19
9.11x10-28 0.0006=
0
Particle Location
Proton
Inside
nucleus
Mass
(amu)
Atomic Number
•Given the symbol (Z)
•Represents the number of protons in an atom
•The atomic number also represents the number of
electrons in a neutral atom of that element.
How many protons and electrons in
the following atoms:
1. Na
2. Pb
3. Os
Ions (Atoms with charge)
• An atom that has either lost or gained one or more electrons.
• Gaining electrons means more negative than positive charges, so
the ion is (-)
• Loosing electrons means more positive than negative charges, so
the ion is (+)
How many protons and electrons does a
magnesium atom have?
What will the charge be if it loses 2 electrons?
No. of protons: 12 (+)
No. of electrons: 10 (-)
Charge of Ion 2+
Write it like this:
Mg2+
Practice
Ion
Protons
Electrons
Cu²+
29
27
F-
9
10
• YOU WILL NEED:
–CALCULATOR
–NOTEBOOK
–PERIODIC TABLE
Learning Target
•
•
Know how the atomic masses on the periodic
table are calculated using the isotopes of the
element.
Know how to determine the number of protons,
neutrons and electron in an atom or ion.
Particle
Proton
Location
Inside
nucleus
Neutron Inside
nucleus
Electron Outside
nucleus
Charge(C)
Mass (g)
Mass
(amu)
1.602 x 10-19 1.673x10-24 1.0073=
1
0
1.675x10-24 1.0087=
1
-1.602 x 10-19 7.109x10-28 0.0006=
0
Atomic Mass
• The mass of an atom is determined using the number
of protons and neutrons in it. (electrons are ignored)
• Since the masses of atoms are so small in conventional mass units,
like grams, we use a unit that is equivalent to the mass, in grams, of a proton.
Atomic Mass Units (amu):
roughly equal to the mass of a proton or neutron.
**the mass of an atom is measured in amu’s
1 amu = 1.66x10-24g
Isotopes
• Isotopes are atoms that have the same number of
protons but different numbers of neutrons
In nature, elements are almost always found as a
mixture of isotopes
Penny Isotopes
Analogy the pennies are different atoms
of the element penny (Pe).
Step #1 Mass of pennies
1. Record the total number of pennies in your container.
2. Separate your penny atoms into 2 categories:
1. 1982 and earlier
2. Later than 1982
3. In 2 data tables (1 for pre-1982 and 1 for post-1982) record
the year and mass of each individual penny.
Some years may be duplicated – record each penny
individually.
Step #2 Averages
• Calculate the average mass of the pennies in your
sample that are 1982 or earlier. This is isotope #1
• Calculate the average mass of the pennies in your
sample that are post-1982. This is isotope #2
Step #3 Percentages
• Calculate the percentage of pennies that are
pre1982 pennies in your container.
• Calculate the percentage of pennies that are post
1982 in your container.
**KEEP THESE IN DECIMAL FORM.
(0.47 not 47%)
Step #4 Calculate the Average
Atomic Mass
• Use the formula:
Average Atomic Mass = (decimal % of 1st Isotope
x Average Mass of 1st Isotope) + (% of 2nd
Isotope x Average Mass of 2nd Isotope)
*Use decimal form of percentage in calculation. .50 not 50%
Atomic mass: weighted average of the
masses of the existing isotopes of an
element.
Atomic Number/
number of protons
Atomic mass
HOW ARE PENNIES AN
ANALOGY FOR ISOTOPES?
• What was Dalton’s 2nd Postulate? (page 92)
• All atoms of a given element are identical, but they differ
from those of any other element.
• Was it correct?
Hmmm
Complete Chemical Symbols
Mass number
141
2+
Ba
56
Charge
Atomic number
Number of protons = Atomic #
Number of neutrons = Mass # - Atomic #
Charge = Atomic # – Number of electrons
Complete the Table
Chemical
Symbol
No. of
Protons
No. of
Electrons
No. of
Neutrons
46
45
50
14
29
Atom or
Ion?
90 2+
38Sr
Atom
• YOU WILL NEED:
–CALCULATOR
–NOTEBOOK
–PERIODIC TABLE
–3-3 Apply Worksheet
WARM UP
• What is the atomic mass unit of a proton?
Neutron? Electron?
• What is the atomic mass of an element represent?
Practice
• What is the chemical symbol for the ion with 13
protons and 10 electrons?
• What is the chemical symbol for the ion with 7
protons and 10 electrons?
• How many protons and electrons are present in
the S2- ion?
• How many protons and electrons in Li+ ion?
• Mass Number – the sum of an isotope’s
protons and neutrons.
• To name an isotope using chemical
symbols, simply place the atom’s mass
number to the upper left of the element
symbol.
• For example 37Cl.
Complete the Table
Chemical
Symbol
No. of
Protons
No. of
Electrons
No. of
Neutrons
46
45
50
14
29
Atom or
Ion?
90Sr2+
38
Atom