1. Ch 11 Introduction to Atoms

2. The Beginning of Atomic Theory
Democritus & Aristotle
Can you cut a piece of paper in half and cut those halves in half and continue until you are left with 1 particle?
If you could do this you would end up with what Democritus called an _________= ______________________
Aristotle _____________ with democritus’s idea. He believed that ___________________________________
Who was correct? Aristotle or Democritus??

3. The Beginning of Atomic Theory
____________________was correct!
Matter is made of particles which we call ___________.
Atom -

4. The Beginning of Atomic Theory
Dalton – 1803
Dalton’s atomic theory was based on _________________!
All substances are made of ______
Atoms are small particles that cannot be _____, _______, or _________.
Atoms of the same element are _________ and atoms of different elements are _________.
Atoms join with other atoms to make _____ substances.

5. The Beginning of Atomic Theory
New information didn’t quite fit with _______ ideas. His atomic theory had to be _________.
Thomson- 1897
Discovered the ____________ charged particles
There are __________ inside the atom. Atoms can be broken down further. (Dalton thought atoms were solid spheres – so he’s wrong)

6. CATHODE-RAY TUBE A positively charged plate was attracted to a ______.
Therefore, the beam must be made up of ________ charges.
Thomson concluded these negative charges are _______ in every kind of _______.

7. The Beginning of Atomic Theory
________- A subatomic particle that has a negative charge.
Thomson described his model of the atom like plum pudding. Today you might call it the ______________ _____ model. (with electrons represented by _________________.)

8. The Beginning of Atomic Theory
Rutherford- 1909
Rutherford was a _____________ of Thomson’s. He tried to help prove Thomson theory was _______ and ended up proving him ______!
He aimed a beam of small, _________________ (α particles) at a thin piece of gold foil.
Photo paper behind the gold recorded where the charged particles hit.
Surprising Results
He thought the particles would _______________ the gold in a straight line.
Some particles were ________. Some shot right ______.

9. Rutherford’s Gold-Foil Experiment
Rutherford determined an atom must be mostly ______ ______ with a tiny part made of highly dense material.

10. Rutherford’s Model
________ – The centrally located, tiny, extremely dense positively charged part of an atom.

11. The Beginning of Atomic Theory
Bohr – 1913
Niels Bohr proposed that electrons move around the nucleus in _______________________________.
Electrons can jump from path to path but cannot exist in _____________ paths.
Think of ________ on a ladder. You can stand on the rungs, but not ________ the rungs.
Or think of planets in our solar system – they do not stray off the set path or ___________.

12. The Modern Atomic Theory
Schrӧdinger and Heisenberg
Electrons ________ travel in definite paths as Bohr suggested.
The exact path of the electron ______ be predicted.
There are regions where it is likely to be found called ______ __________.

13. 4.2 The Atom How small is an _____? The Nucleus
A penny contains __________ atoms. (20,000,000,000,000,000,000,000 atoms)
An atom is made up of _______, _______, and _________.
The Nucleus
Protons –
The mass of protons are measured in atomic mass units (amu). Each proton has a mass of __________
_________- Particles in the nucleus that have ___ electrical charge.
Neutrons have a mass of 1 amu. (Same as _________)

14. The Atom Outside the nucleus
_________ are found outside the nucleus. They have a _______ charge. They have a mass of almost _____.
If the number of protons __________ the number of electrons, the atom is ______________

15. HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER?
Atoms of different elements have different numbers of ____________.
No two elements have the same _____________.
Atomic number is the number of ________ in an atom. All atoms of the _____________ have the _________ atomic number.

16. HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER?
So how do we figure out the number of neutrons for an atom?
The number of _____________ = the number of _______________
Mass number –
The mass number does not include the mass of ____________ because they are so ___________and have very little effect.

17. HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER?
Where do you find these numbers? 
On the ____________________ !
C C C  
# of neutrons = _________ - _________
# of neutrons in C = ____ - ____ C
P+ =
No=
E- =
______
# __ + # __
___
______
# __
___

18. HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER?
Mass #
Atomic #
Protons
Neutrons
Electrons Li Be B C N O F Na k

19. DRAWING BOHR MODELS OF ATOMS
Draw the nucleus and label with #p & #n
Draw electron orbitals
1st orbital can have ______ electrons only
2nd and 3rd ring can each have ______electrons
Fill – _____________________
Inner rings must be filled first before any electron enters a higher ring!!!!!
Examples:

20. Changing Atoms
If you change a persons hair color does it change who they are? Weight?
What subatomic particle determines an atoms identity?___________
Therefore, the number of electrons and neutrons can change in the atom and it is still the same atom.
If the number of protons __________ the number of electrons, the atom is ______________
If the number of protons ___________ the number of electrons, the atom becomes charged and we call it an _______.
 Positively charged ions –
Negatively charged ions -

21. ISOTOPES
_________- Atoms that have the same number of protons, but have different numbers of neutrons.
Examples:
Hydrogen -1 and Hydrogen -2
Naming Isotopes
Write the __________ of the element, followed by a hyphened and the _____________________ of the isotope.
Ex. A hydrogen atom with 1 proton and 0 neutrons
A hydrogen atom with 1 proton and 1 neutron

22. ISOTOPES
Mass Number – The sum of the _________________ in an atom. (__________ are not included.)
Mass # = protons + neutrons
Atomic Mass – The _____________ of the masses of all the ___________ occurring isotopes of that element.

23. Solving the Atomic Mass
Ex: Skittles consist of Orange – 1 which is 25% of the Skittles and Red – 2 which is 75% of skittles.
Step1: change percents to decimals.
Step 2: multiply the decimal by the mass
Step 3: add the two answers together

24. Solving for Atomic Mass
Ex: Chlorine-35 which is 76% of the Chlorine atoms and Chlorine-37 which is 24% of Chlorine atoms.
Step1: change percents to decimals.
Step 2: multiply the decimal by the mass
Step 3: add the two answers together