1. Copy the following Essential Question!!
Please pick up a Atomic History & Structure packet and periodic table off my desk
Copy the following Essential Question!!
EQ: How are the subatomic particles of an atom calculated? How is the Bohr model drawn for elements?

2. The Building Blocks of Matter: Atoms- - - + + + + - - + + - - -

3. Atoms
Smallest possible unit into which matter can be divided, while still maintaining its properties.
Made up of:
protons
neutrons
electrons - +
For example, what is the
smallest possible unit
into which a long essay can be
divided and still have some meaning? - + + - + + - -

4. Atoms are so small that…
it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen.
if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping-pong ball
a human hair is about 1 million carbon atoms wide.
a typical human cell contains roughly 1 trillion atoms.
a speck of dust might contain 3x1012 (3 trillion) atoms.
it would take you around 500 years to count the number of atoms in a grain of salt.
C-C-C-C-C-… + 999,995 more
1 trillion atoms  .
Is made of approximately 3 trillion atoms
Just one of these grains

5. + Protons (+) Positively charged particles Located in the NUCLEUS
The identity of the atom…they NEVER change!
Equal to the atomic number of the atom
Equal to the number of electrons in a neutral atom
Protons + Neutrons = Mass Number + - +

6. Neutrons Neutrons = Mass Number - Protons+ -
Neutral particles; have no electric charge
Located in the NUCLEUS of the atom
Neutrons = Mass Number - Protons

7. - Electrons (-) Negatively charged particles
Found outside the nucleus of the atom, in the electron shells
Move so rapidly around the nucleus that they create an electron cloud
Mass is insignificant when compared to protons and neutrons
Equal to the number of protons in a neutral atoms
Involved in the formation of chemical bonds
2n2 to determine number of electrons per shell + - -

8. + The Atom’s “Center” - - -
Protons and neutrons are grouped together to form the “center” or nucleus of an atom.
Notice that the electrons are not apart of the nucleus + - - -

9. What would be the atomic number of this atom?
The number of protons in the nucleus of an atom -
What would be the atomic number of this atom? + - -

10. + Mass Number + What would be the mass number of this atom? - - -
The total number of PROTONS + NEUTRONS in an atom’s nucleus
Expressed in Atomic Mass Units (amu)
Each proton or neutron has a mass of 1 amu
What would be the mass number of this atom? - +
 3
 4 + -
3 protons + 4 neutrons = a mass number of 7 amu
Why did we not account for the electrons when calculating the mass number? (Like counting the weight of a flea on a dog) -

11. Short hand form AZ Notation Ex. AZ X A = mass number Z = atomic number
X = Element Symbol
So…126C shows that Carbon has an atomic number of 6 (6 protons) and a mass number of 12 (6 protons and 6 neutrons)
147N: How many protons? ____ Electrons? ____ Neutrons?__
3216 S: Protons? _____ Electrons? ______ Neutrons? ____
3517Cl: Protons? ______ Electrons? _________ Neutrons? _____

12. Sub-Atomic Particles Weight Comparison (protons, neutrons, electrons)
Neutron = x10-27 kg Proton = x10-27 kg Electron = x10-31 kg - - +
1839 electrons = 1 neutron
1836 electrons = 1 proton +
How do you think the mass of a neutron
compares to that of a proton?
1 neutron ≈ 1 proton

13. Hydrogen (H) Atom - Notice the one electron in the first orbital = 1 +
= 0 -
How many
more electrons
can fit in the 1st
orbital/ level?
2n2 +
Even though there are no neutrons present,
Hydrogen is still considered an atom

14. Oxygen (O) Atom
Notice the two electrons in the first orbital/level and the six in the second + -
= 8
How many
more electrons
can fit in the 2nd
orbital/ level? - - - + + + + - - + + - - -

15. Sodium (Na) Atom
Notice the two electrons in the first orbital/level, eight in the second, and one in the third + -
= 11
= 12 - - -
How many
more electrons
can fit in the 3rd
orbital/ level? - + + + + - - - + + - - - -

16. Isotopes
All atoms of the same element have the same number of protons; however, atoms of the same element with different numbers of neutrons are called isotopes.
Notice that each of these atoms have one proton; therefore they are all types of hydrogen. They just have a different mass number (# of neutrons). - - + + + -
Hydrogen (Protium)
Hydrogen (Deuterium)
Hydrogen (Tritium)

17. Isotopic Notation…
Atoms with extra neutrons are like a person born with extra fingers! Still human, but a little bit different!
Often, atoms with extra neutrons are unstable and break apart (called radioactivity!). The more extra neutrons, the more unstable they are.
Element Name – mass number OR Element Symbol – mass number
For example, all carbon atoms have 6 protons (definition of carbon.)
Most carbon atoms have 6 neutrons (mass number of 12.)
Carbon – 12 OR C – 12
But some carbon atoms have 8 neutrons, giving them an mass number of 14.
Carbon – 14 OR C-14

18. What would be the atomic mass (≈) of Hydrogen if these three isotopes
Isotopes & Atomic Mass
So far, we’ve been talking about “mass number”…just Protons + Neutrons
The “atomic mass” is similar; it is the decimal number found in the periodic table.
This number reflects the fact that there are isotopes with different numbers of neutrons.
The atomic mass is the weighted average of the masses of all the naturally occurring isotopes of an element
The average considers the percent abundance of each isotope in nature
Take the percent and convert it into a decimal
Multiple the decimal by its coordinating mass number
Add the numbers together - + + + - -
Hydrogen (Protium)
Mass # = 1 amu
Hydrogen (Deuterium)
Mass # = 2 amu
Hydrogen (Tritium)
Mass # = 3 amu
What would be the atomic mass (≈) of Hydrogen if these three isotopes
were found in the following percentages (99.9%, 0.015%, 0%) respectively?

19. Calculating Average Atomic Mass
Ex. An element has 3 isotopes: 24.1% of all the isotopes have a mass of amu, 48.7% have a mass of 74.61, and 27.2% have a mass of What is the average atomic mass of the element?
Convert percent to a decimal by moving the decimal 2 places to the left.
Multiple each % by its mass
Add together

20. How to determine most abundant isotope
Calcium has 3 isotopes. One has a mass of 35amu, another 41amu, and another 40amu. Which isotope is the most abundant?
Look at the atomic mass to determine most abundant isotope!

21. Homework: Build these atoms and complete Structure and mass Worksheet
Building Atoms
Homework: Build these atoms and complete Structure and mass Worksheet
Atoms
Protons
Neutrons
Electrons
Carbon 6
Beryllium 4 5
Oxygen 8
Lithium 3
Sodium 11 12

22. Atom Builder
Using the interactive website link below, practice building atoms.
Using the classzone.com link below, click on the “Build an Atom” simulation and practice building atoms.