Download Atomic Structure-1

2/10 Bell Work

Solve the word puzzles.
2/10 Schedule

Finish Work, Energy, Heat Test

Black Box Activity
Assignments:
“Black Boxes”

DO NOT OPEN, but attempt to figure out what is in the
container.

Compare answers with other groups.
Can’t see the objects
or atoms…
2/13 Bell Work

Solve the word puzzles.
2/13 Schedule

Finish Work, Energy, Heat Test?

Notes Ch 4.1 “Development of Atomic Theory”-4.2
“Structure”

Concept Review Ch 4
Assignments:
1. Concept Review Ch 4 “Atoms” - TBA
Ch 4.1 “Development of
Atomic Theory”
Objectives
〉
Describe how Democritus, Dalton, Thomson,
and Rutherford’s ideas contributed to
understanding of atoms.
〉
Compare/contrast different models of the
atom.
Beginning Atomic Theory
Democritus
〉
〉
〉

4th Century BCE
Greek philosopher
Universe was made of indivisible,
indestructible units called atoms.
Democritus did not have evidence for his atomic
theory.
Dalton’s Atomic Theory
Dalton (1808)
〉 Atoms of an element are exactly alike,
indivisible, and join to form compounds.
〉
Used experiments and Evidence

Law of definite proportions: A chemical compound always
contains the same elements in exactly the same proportions by
weight or mass.
Thomson’s Atom
Subatomic particles discovered (1897)
〉 Experiments with cathode-ray tubes.
〉
〉
Run electricity through gas in a sealed tube.
Noticed a stream of particles.
Vintage cathode-ray tube
If the particles bend AWAY from a
negative charge, what charge are
they?
Thomson’s Atom
Thomson’s Model

Discovered negative particles… electrons.

He called his model the plum-pudding model.
Atoms are NEUTRAL, so there must be
positive AND negative particles.
Plum-pudding model.
Rutherford’s Atom
Rutherford’s Planetary Model (1911)
〉 Intended to study Thomson’s model.
〉 Conducted an experiment with gold foil and
alpha particles.
〉
Expected alpha particles to pass though, BUT
they were deflected.
Rutherford’s Atom
Rutherford discovered the nucleus.

Nucleus: an atom’s central region, which is made up of
protons (+) and neutrons (0)
Ch 4.2 “The Structure of
Atoms”
Objectives
〉
Compare/contrast protons, neutrons, and electrons.
〉
Distinguish between atoms and isotopes.
〉
Identify the unit for atomic mass.
Structure Review
Atoms are very small, and they are made up of even smaller
subatomic particles.
Structure Review
1.
In the diagram, A is the center of an atom. What is the center of an
atom called?
2.
The center of an atom is made up of positively charged particles
and particles that have no electrical charge. Name the two
particles.
3.
Negatively charged electrons are found in clouds outside the
center of an atom. Why are electrons attracted to the center of the
atom?
Subatomic Particles
3 Major subatomic particles
〉
〉
Protons, neutrons, and electrons
Differ in charge, location in atom, and mass.
Subatomic Particles
Protons and Electrons

Each element has a unique number of protons.

Atoms have no overall charge.
 Protons – Electrons = 0.

Electric force holds the atom together.
 Positive protons are attracted to negative electrons.
Atomic and Mass Number

The atomic number equals the number of protons.

The mass number equals the total number of subatomic
particles in the nucleus (protons and neutrons)
Mass
Atomic Number and Mass
Number, continued
Isotopes
Isotopes: Atoms of the same element with
different numbers of neutrons.
Isotope designations – Hydrogen 1, H-1, and 1H
Isotopes, continued
Some isotopes are more common than others.
 radioisotopes: unstable isotopes that emit radiation
and decay into other isotopes
Calculate neutron number.
 neutrons = mass number – atomic number
2/14 Bell Work
Heigh ho, heigh ho, it’s off to school you go…Disney released
its first full-length animated film in 1938.

Name the film.
2/14 Schedule

Finish Work, Energy, Heat Test?

Notes Ch 4.2 “Structure”

Atomic Basics packet
Assignments:
1. Concept Review Ch 4 “Atoms” – TBA
2. Atomic Basics packet due THURSDAY
Atomos Atomos
Watch the video clip, and be able to answer the following
questions.

Which of your vocabulary terms came from “atomos”?

Name and describe AT LEAST two atomic models we have
already talked about.

Name and describe one of the more modern atomic models.
Atomic Masses
Unified atomic mass unit: a unit that describes the mass of an
atom or molecule;



Defined as 1/12 the mass of a carbon atom with mass
number 12
aka mass of a proton or neutron
symbol, u or amu
Atomic Masses
Average atomic mass is a weighted average.
– Isotope abundance
determines the average
atomic mass.
– Ex: Chlorine-35 is more
abundant than chlorine-37,
so chlorine’s average atomic
mass (35.453 u) is closer to
35 than to 37.
Weighted Average
Problems
Atomic masses are weighted averages that take into account the
number of items and the value of each.

A student has 4 As, 10 Bs, 3 Cs, and 1 F. Use a four point
scale to figure out their average grade.

Sabrina has 4 quarters, 6 dimes, 9 nickels, and 15 pennies.
What is the average value of the coins?
Atomic Masses
The mole is useful for counting small particles.

mole: the SI unit used to measure the amount of a substance
whose number of particles is the same as the number of atoms of
carbon in exactly 12 g of carbon-12 (abbreviation, mol)

1 mol = 602, 213, 670, 000, 000, 000, 000, 000 particles

This number, 6.02 × 1023, is called Avogadro’s number.
Atomic Masses, continued
Moles and grams are related.

molar mass = the mass in grams of one mole


Ex: 1 mol of carbon-12 atoms has a mass of 12.00 g, so the
molar mass of carbon-12 is 12.00 g/mol
You can convert between moles and grams.
Modeling Atoms and
Isotopes
Work with desk groups.

Pick blocks to represent protons, neutrons, and electrons.

Model the following atoms and isotopes. Be sure to put the
right number of each in the correct place.





Helium-4
Carbon-13
Beryllium (use PT)
Oxygen (use PT)
Have each model checked then try the next.
Math Skills
Converting Moles to Grams
Determine the mass in grams of 5.50 mol of iron.
1. List the given and unknown values.
Given:
Unknown:
amount of iron = 5.50 mol Fe
molar mass of iron = 55.84 g/mol Fe*
mass of iron = ? g Fe
*Use the periodic table to find molar mass.
Average atomic mass of an element is equal to the
molar mass.
Math Skills
2. Write down the conversion factor that converts moles to
grams.
The conversion factor you choose should have what you
are trying to find (grams of Fe) in the numerator and what
you want to cancel (moles of Fe) in the denominator.
55.84 g Fe
1 mol Fe
3. Multiply the amount of iron by this conversion factor, and
solve.
55.84 g Fe
5.50 mol Fe ´
= 307 g Fe
1 mol Fe
Compound Masses
Compound molar masses

Add the molar masses of the atoms in a molecule.

Example: finding the molar mass of water, H2O



molar mass of O = 16.00 g/mol
molar mass of H = 1.01 g/mol
molar mass of H2O = (2 × 1.01 g/mol) + 16.00 g/mol = 18.02
g/mol
Interpreting Chemical
Formulas
Letters = symbol for elements
Subscripts = number of that
element/group in the compound
Coefficients = number of compound
groups
2 hydrogen molecules + 1 oxygen molecule
make 2 water molecules
Measuring Out Moles

Use a Periodic Table to find masses of the atoms &
compounds.

Use a balance to see what a mole of each looks like.

Have your masses checked and turn in work.
Substances:

Paper clips (Iron)

Sugar (C11H12O11)

Baking soda (NaHCO3)