1. Topic 1
The Atom

2. Topic 1-Outline Parts of the Atom a. Proton b. Neutron c. Electron
d. Rutherford’s Gold Foil Experiment
2. The Structure of the Atom
a. Mass number
b. Number of protons
c. Number of neutrons
d. Number of electrons
e. Atomic number
f. Ions
Isotopes
Atomic Mass
-be able to calculate
Electron Configuration
a. Know the diagonal rule
b. Three methods
c. Ground state vs. excited state
6. Types of Matter
a. Homogeneous vs. heterogeneous matter
b. Pure Substances
c. Mixtures
d. Distinguishing between mixtures and compounds
i. Filtering
ii. Chromatography
iii. Distillation

3. Definitions/Terms to Know
1. Proton
A positively charged subatomic particle found in the nucleus of an atom.
It has a mass of 1 amu and
a positive charge

4. 2. Neutron
A subatomic particle with no (neutral) charge and a mass of 1 amu;
found in the nucleus of an atom

5. Protons + neutrons in the nucleus
3. Nucleons
Protons + neutrons in the nucleus
of an atom

6. 4. Electron orbiting around the nucleus.
A negatively charged subatomic particle found
orbiting around the nucleus.
It has no mass and a negative charge
In the modern theory,(aka the wave-mechanical model)
the electron has both properties of a wave and particle.
This is referred to as the wave-particle duality of
the electron

7. Models of the Atom
1. Dalton (1803)-pictured atoms as tiny, indestructible particles, with no internal structure.
Thomson (1897)-electrons embedded in a sphere of positive electrical charge
Plum pudding model

8. Electrons move around the nucleus. Atom is mostly empty space.
Rutherford (1922)-finds that an atom has a small, dense, positively charged nucleus.
Electrons move around the nucleus.
Atom is mostly empty space.
Never mentions neutrons.

9. Rutherford’s Gold Foil Experiment
An atom is mostly empty space.
It consists of a positively charged,
dense center (nucleus) with
electrons found orbiting the nucleus.
He never mentioned neutrons.

10. 4. Bohr (1913)-the electrons move in circular orbits at fixed distances from the nucleus

11. 5. Schrodinger (1926)-describes the motion of electrons
in atoms. His work leads to the electron cloud model.
Orbital-region of space in which there is a high probability
of finding an electron

12. The Atom

13. Mass Number Number of Protons
Equal to the # protons + # neutrons
Must be a whole number
Equal to the atomic mass rounded to the
nearest whole number
Number of Protons
Equal to the atomic number
Is also the nuclear charge

15. How to find the number of protons, electrons, neutrons,
atomic number, mass number
# protons = atomic number (look on Periodic Table)
# neutrons = mass number - # protons
mass number = # protons + # neutrons or
atomic mass rounded to nearest whole number
(depending on the information given)
# electrons = # protons (if neutral)
Atomic mass = look on Periodic Table
The weighted average of the masses of the
naturally occurring isotopes of the element

17. 4 different ways of element notation1.
2. 4He
3. He-4
4. Helium-4

18. Ion-an atom or group of atoms that has a positive or negative charge
Negative ion (anion)-gained electrons
ex. S-2-gained 2 electrons
PO4-3-gained 3 electrons
Positive ion (cation)-lost electrons
ex. Fe+3-lost 3 electrons
NH4+1-lost 1 electron

19. Element/Ion C-12 C-13 C-14 #p #n #e Atomic mass At. # Mass #
Isotope-atoms of the same element that have the same atomic
number (same # of protons) but different mass number
due to a different number of neutrons
Element/Ion
C-12
C-13
C-14 #p #n #e
Atomic mass
At. #
Mass # 6 6 6 6 8 7 6 6 6
12.011
12.011
12.011 6 6 6 14 12 13

20. So…let’s put it all together and attempt to fill in a chart
Element/
Ion
Atomic
Mass
No.
# p
# n
# e Ca
40.08 20 20 20 20 40 51 71 51
122 51 Sb
N-3 7 7 7 10 14 52
Te+6 52 76
127.60 46
128

21. Element Mass # Atomic # p #n # e Ar-36 36 39.948 18 Ar-38 38 20 Ar-40
Watch out for isotopes. The atomic mass and the
mass number will not correspond to each other
Element
Mass #
Atomic
# p #n
# e
Ar-36 36
39.948 18
Ar-38 38 20
Ar-40 40 22

22. Remember our definition of atomic mass-the weighted
average of the masses of the naturally-occurring
isotopes of that element.
So…how do they determine an atomic mass?
Ex. Cl-35 has an abundancy of % and
Mass of
Cl-37 has an abundancy of 24.23% and
Mass of
Since it is a weighted average:
(34.969)(75.77) + (36.966)(24.23) =
100
Check your periodic table now!

23. The location of an atom’s electrons is called electron configuration
It becomes important to chemists to know the location of an atom’s electrons.
The location of an atom’s electrons is called
electron configuration
There are 3 methods:
Diagonal Method
Arrow Method
Lewis Dot
All three methods depend on the fact that you know
The Diagonal Rule

24. The Diagonal Rule

25. What does each number/letter represent?
Maximum no. of
< electrons
(can have less)
Principle
Energy level 
(1-7) ^
Sublevel
(s, p, d or f)

26. The part of the atom exclusive of its valence electrons
Kernel-
The part of the atom exclusive of its valence electrons
(the nucleus + all inner electrons)
Valence electrons-
The electrons in the outermost shell (valence shell) of an atom

27. The condition of an atom or ion in which the electrons
Ground state
The condition of an atom or ion in which the electrons
occupy the lowest available energy levels
Excited state
The condition that exists when the electrons
of an atom occupy higher energy levels while lower
energy levels are vacant
Ground state
Excited state

28. How does an electron become excited?
Electrons absorb energy and temporarily move
to a higher energy level. The electron quickly returns
to a lower available level emitting the same amount of
energy it absorbed to go to the higher energy level.
This energy is seen as light.
While the light appears as one color, it is actually composed of many different wavelengths, each of which is seen as a different line when viewed through an instrument called a spectroscope.

30. and these spectra are used to identify elements
Each atom has its own distinct pattern of emission lines (or bright line spectrum)
and these spectra are used to identify elements

31. 3 Types of Matter
1. Element-
The simplest form of matter that has a unique set of properties; an element cannot be broken down into simpler substances by chemical means.
A substance that contains two or more elements chemically combined in a fixed proportion.
Can be separated by chemical means
2. Compound-
3. Mixture-
A physical blend of two or more
substances that are not chemically
combined. Can be separated by physical
means.

32. that we can refer to as substances? ANSWER: ELEMENTS & COMPOUNDS
Matter that has uniform and definite composition;
also called pure substance
Based on our definitions of element, compound, mixture and substance, what are the only things
that we can refer to as substances?
ANSWER: ELEMENTS & COMPOUNDS

33. Based on the distribution of their components, elements
compounds and mixtures can be classified as either
homogeneous or heterogeneous
Homogeneous-a mixture that is uniform in composition;
components are evenly distributed and not easily
distinguished.
Heterogeneous-a mixture that is not uniform in composition; components are not evenly
distributed throughout the mixture.

34. Elements
Copper
Nickel

35. Compounds
Aluminum oxide
Sodium chloride

36. Mixtures
Rocky road ice cream
Soil
suspension
Vinegar
solution

37. Based on our definitions and the pictures we saw,
what types of matter are homogenous?
Elements
Compounds
Mixtures-solutions only
Based on our definitions and the pictures we saw,
What types of matter are heterogeneous?
Mixtures-but not solutions

38. How do we describe matter and the changes that matter undergoes?
We describe matter based on its physical and
chemical properties and the physical and chemical
changes that it undergoes.

39. Physical Property-
Those characteristics that can be
observed without the production of a
new substance.
Ex.: color
odor
taste
hardness
density
melting point
boiling point
conductivity
ductile (can be drawn into wires)
malleable (can be hammered into sheets)
luster (shine)

40. Chemical property-
Characteristics that describe how
the substance interacts (or fails
to interact) with other substances
to produce new substances.
Ex.: reactivity
flammability
combustibility
(no longer have the original substance and can’t get it back)

41. Physical Change-
When one or more physical properties
of a substance are changed but
without any change in the substance’s
chemical properties or composition.
Ex.: change of color
grinding of substance
magnetizing of iron
melting
boiling
dissolving

42. Chemical change-
Any change that results in the
production of one or more substances
that differ in chemical properties and
composition form the original substance
Ex. rusting of iron
souring of milk
burning of paper

43. Law of Conservation of Energy-
In any chemical or physical process, energy is neither
created nor destroyed
Law of Conservation of Matter/Mass
In any physical or chemical reaction, mass is conserved;
mass can be neither created nor destroyed.
Mass of reactants = Mass of products
2H O2  2H2O
4 g
32 g
36 g

44. Physical Means of Separation
Filtration-a process that separates a solid from the liquid in a heterogeneous mixture

45. The separation of mixtures into their constituents by
Chromatography
The separation of mixtures into their constituents by
preferential adsorption

46. Distillation/Fractional Distillation
A process used to separate dissolved solids from a
liquid, which is boiled to produce a vapor that
is then condensed into a liquid