1. What components make-up the Atom?
Atomic Structure
What components make-up the Atom?

2. How do you study something that you cannot see it?
Similar to how you might study a gift-wrapped present, scientists often study things that cannot be seen with the naked eye.

3. Notes: Defining The Atom

4. Early Models Of The Atom
An atom is the smallest particle of an element that retains its identity in a chemical reaction.

5. Early Models 0f The Atom- Democritus
Democritus reasoned that atoms were indivisible and indestructible.
Although, Democritus’s ideas agreed with later scientific theory, they did not explain chemical behavior
They also lacked experimental support because Democritus’s approach was not based on the scientific method.

6. Early Models 0f The Atom-Dalton
Dalton studied the ratios in which elements combine in chemical reactions.
The result of his work is known as Dalton’s atomic theory.

7. Early Models of the Atom
Dalton’s Atomic Theory
All elements are composed of tiny indivisible particles called atoms.
Atoms of element A

8. Early Models of the Atom
Dalton’s Atomic Theory
Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
Atoms of element A
Atoms of element B

9. Early Models of the Atom
Dalton’s Atomic Theory
Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.
Mixture of atoms of elements A and B

10. Early Models of the Atom
Dalton’s Atomic Theory
Chemical reactions occur when atoms are separated from each other, joined, or rearranged in different combinations. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction.
Compound made by chemically combining atoms of elements A and B

11. Notes: Structure of the Nuclear Atom
How did scientists determine the structures that are inside an atom?
Doctors often use X-rays to see bones and other structures that cannot be seen through your skin. Scientists use many methods to “see” inside an atom.

12. Subatomic Particle
Three kinds of subatomic particles are electrons, protons, and neutrons.

13. Subatomic Particles-Electrons
In 1897, the English physicist J. J. Thomson (1856–1940) discovered the electron.
Electrons are negatively charged subatomic particles.

14. Subatomic Particles- Electrons
Thomson performed experiments that involved passing electric current through gases at low pressure.
He sealed the gases in glass tubes fitted at both ends with metal disks called electrodes.
The electrodes were connected to a source of electricity.

15. Subatomic Particles- Electrons
One electrode, the anode became positively charged.
The other electrode, the cathode, became negatively charged.

16. Subatomic Particles- Electrons
The result was a glowing beam, or cathode ray, that traveled from the cathode to the anode.
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17. Subatomic Particles- Electrons
Thomson found that a cathode ray is deflected by electrically charged metal plates.
A positively charged plate attracts the cathode ray, while a negatively charged plate repels it.

18. Review The Following Experiments
John Dalton
J.J Thompson
Be able to describe what they discovered and their experiments

19. Notes: The Atomic Nucleus
This model of the atom turned out to be short-lived, however, due to the work of a former student of Thomson, Ernest Rutherford (1871–1937).
Born in New Zealand, Rutherford was awarded the Nobel Prize for Chemistry in His portrait appears on the New Zealand $100 bill.

20. Rutherford’s Gold-Foil Experiment
They devised the gold-foil experiment.
Their test used alpha particles, which are helium atoms that have lost their two electrons and have a double positive charge because of the two remaining protons.

21. Rutherford’s Gold-Foil Experiment
What was surprising is that a small fraction of the alpha particles bounced off the gold foil at very large angles.

22. Rutherford’s Gold-Foil Experiment
Based on his experimental results, Rutherford suggested a new theory of the atom.
In the nuclear atom, the protons and neutrons are located in the positively charged nucleus.
Protons and Neutrons account for the mass of the atom
The electrons are distributed around the nucleus and occupy almost all the volume of the atom.

23. What components make-up the Atom?
Atomic Structure
What components make-up the Atom?

24. Notes: Distinguishing Among Atoms
Thing we learned. . .
The atom is divisible. Is it made of subatomic particles.
List all subatomic particle in your notebook and their charges.

25. Atomic Number and Mass Number
What makes one element different from another?
Just as there are many types of dogs, atoms come in different varieties too.

26. Atomic Number and Mass Number
Elements are different because they contain different numbers of protons.
An element’s atomic number is the number of protons in the nucleus of an atom of that element.
The atomic number identifies an element.

27. Atoms of the First Ten Elements
For each element listed in the table below, identify the similarities and difference between each element for each .
Atoms of the First Ten Elements
Name
Symbol
Atomic number
Protons
Neutrons
Mass number
Electrons
Hydrogen H 1
Helium He 2 4
Lithium Li 3 7
Beryllium Be 5 9
Boron B 6 11
Carbon C 12
Nitrogen N 14
Oxygen O 8 16
Fluorine F 10 19
Neon Ne 20
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28. Atomic Number and Mass Number
Atoms are electrically neutral.
Thus, the number of electrons (negatively charged particles) must equal the number of protons (positively charged particles).
Discuss: The element nitrogen (N) has an atomic number of 7. How many protons and electrons are in a neutral nitrogen atom?

29. Atomic Number and Mass Number
The total number of protons and neutrons in an atom is called the mass number.
If you know the atomic number and mass number of an atom of any element, you can determine the atom’s composition.
Ex. Protons + Neutrons= Mass Number

30. Determining the Composition of an Atom
Sample Problem 4.2
Determining the Composition of an Atom
How many protons, electrons, and neutrons are in each atom?
a. Be b. Ne c. Na 9 4 20 10 23 11

31. Isotopes There are three different kinds of neon atoms.
Discussion: How do these atoms differ?

32. Isotopes
Isotopes are atoms that have the same number of protons but different numbers of neutrons.
Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.

33. Atomic Mass
The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element.
A weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature.
Units: amu (Atomic Mass Units)

34. Atomic Mass
Discussion: The atomic mass of copper is amu. Which of copper’s two isotopes is more abundant: copper-63 or copper-65?

35. What components make-up the Atom?
Atomic Structure
What components make-up the Atom?

36. Notes: Revising the Atomic Model
Things we learned
Atoms are made of protons, neutron and electrons
Protons and Neutrons make up the mass of the atom
Electron make up the volume of an atom

37. Energy Levels in an Atom- Bohr Model
Proposed that an electron is found only in specific circular paths, or orbits, around the nucleus.
Each electron has a fixed energy. The fixed energies an electron can have are called energy levels.
To move energy levels, electrons must gain or lose the right amount of energy.

38. Energy Levels in an Atom- Bohr Model

39. Energy Levels in an Atom- Bohr Model
The rungs on this ladder are somewhat like the energy levels in Bohr’s model of the atom.
A person on a ladder cannot stand between the rungs. Similarly, the electrons in an atom cannot exist between energy levels.
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40. The Quantum Mechanical Model
Mathematical Solution to find energy in an electron
The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus of an atom.
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41. The Quantum Mechanical Model
Electron cloud
In the quantum mechanical model, the probability of finding an electron within a certain volume of space surrounding the nucleus can be represented as a fuzzy cloudlike region.
The cloud is more dense where the probability of finding the electron is high.
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42. Atomic Orbitals
An atomic orbital is a region of space in which there is a high probability of finding an electron.

43. How many electrons can it hold?
Atomic Orbitals
Type of Orbital
Number of Orbitals
How many electrons can it hold? S 1 2 P 3 6 D 5 10

44. Atomic Orbitals Summary of Principal Energy Levels and Sublevels
Number of sublevels
Type of sublevel
Maximum number of electrons
n = 1 1
1s (1 orbital) 2
n = 2
2s (1 orbital), 2p (3 orbitals) 8
n = 3 3
3s (1 orbital), 3p (3 orbitals),
3d (5 orbitals) 18
n = 4 4
4s (1 orbital), 4p (3 orbitals),
4d (5 orbitals), 4f (7 orbitals) 32
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45. What components make-up the Atom?
Atomic Structure
What components make-up the Atom?

46. Notes: Electrons Arrangement in a Atom
Things we learned
Electrons have a fixed amount of energy and circulate in a specific path around the nucleus.
Atomic orbitals are where an electron can be found.
Each type of orbital can hold a specific number of electrons.

47. Atomic Orbitals on Periodic Table

48. Electron Configurations
Show the ways in which electrons are arranged in various orbitals around the nuclei of atoms.
Energy and stability play an important role in determining how electrons are configured in an atom.

49. Electron Configuration Rules
Three rules—the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms.

50. Electrons will occupy the lowest energy level first.
The Aufbau principle
Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p
Electrons will occupy the lowest energy level first.

51. Pauli exclusion principle
According to the Pauli exclusion principle, an atomic orbital may have at most TWO electrons.
To occupy the same orbital, two electrons must have opposite spins; that is, the electron spins must be paired.

52. Hund’s Rule
Each orbital is occupied with single electron in each orbital before adding the 2nd electron.

53. Let’s Practice! 
Helium
Nitrogen
Magnesium
Chlorine

54. What components make-up the Atom?
Atomic Structure
What components make-up the Atom?