1. ATOMIC STRUCTURE

2. State Standards
8.3a – Students know the structure of the atom and know it is composed of protons, neutrons, and electrons.
8.7b – Students know each element has a specific number of protons in the nucleus (the atomic number) and each isotope of the element has a different but specific number of neutrons in the nucleus.
8.9a – Plan and conduct a scientific investigation to test a hypothesis.

3. Draw what you think an ATOM looks like.
Warm-Up Activity
Draw what you think an ATOM looks like.
Label nucleus, protons, neutrons, electrons, electron cloud, electron shells.

4. Contents Key Terms Development of the Atomic Theory Quick Lab The Atom
Model of Atom Project

5. What I want to know about Atoms What I learned about Atoms
What I know about Atoms
What I want to know about Atoms
What I learned about Atoms 1 2 3 4 5

6. Key Terms
Atom – The smallest unit of an element that still has the properties of the element.
Electron – A subatomic particle with a NEGATIVE (-) charge.
Nucleus – Central region of atom where Protons and Neutrons are located.
Electron Cloud – Region around the nucleus where electrons are found.
Proton – A subatomic particle with a POSITIVE (+) charge.

7. Key Terms
Atomic Mass Unit (amu) – A unit used to measure the mass of an atom or molecule
Neutron – A subatomic particle with a NEUTRAL charge.
Atomic Number – The number of Protons and Electrons in an atom.
Isotope – An atom with a different number of Neutrons.
Atomic Mass – The sum of the number of Protons and Neutrons in an atom.

8. ATOMIC THEORY

9. Development of Atomic Theory
Beginning of Atomic Theory
Democritus –
400 BCE
Thought that if you cut something in half enough times, you will get a particle that you cannot cut anymore.
John Dalton -
Wanted to know why elements combine in certain ratio’s based on their mass.
In 1803 published the atomic theory
Rutherford’s experiment led to changing of theory.

10. The Beginning of Atomic Theory
Democritus was right a long time before people agreed that matter was made of atoms.
An Atom is the smallest particle into which an element can be broken down to and STILL keep its PROPERTIES.

11. Dalton’s Atomic Theory Based on Experimentation
By late 1700’s scientists had learned that elements combine in ratio based on mass to form compounds.
H2O – Ratio of Hydrogen Mass to Oxygen Mass
2:16 1:8
John Dalton wanted to know why.
His results showed that elements combine in a certain ratio because they are made of atoms.

12. Atoms join with other atoms to make new substances.
Atomic Theory
All substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed.
Atoms of the same element are exactly alike, and atoms of different elements are different.
Atoms join with other atoms to make new substances.

13. Atomic Theory
Dalton’s theory was an important step toward the current understanding of atoms.
In the late 1800’s scientists agreed that Dalton’s theory explained much of what they saw.
Scientists also found information that DID NOT fit Dalton’s Theory.
They conducted more experiments to describe the atom more precisely.

14. Thomson’s Discovery of Electrons
In 1897 British Scientist J.J. Thomson showed that Dalton’s theory was not completely right.
Thomson discovered that there are smaller particles inside the atom.
That means that Atoms can be divided into smaller parts.
He discovered negatively charged particles called ELECTRONS.

15. Thomson’s Discovery of Electrons
Thomson showed that electrons are a part of atoms, but he did not figure out where in the atom they are.
In your notebook, quickly write down where you think electrons are located.
Thomson guessed that the electrons were mixed throughout the atom.
Like chocolate chips in ice cream.
Chocolate Chips - electrons.
Ice Cream - The rest of the atom

17. Rutherford’s Atomic “Shooting Gallery”
In 1909, a former student of Thomson named Ernest Rutherford decided to test Thomson’s theory.
He designed an experiment to study the parts of the atom.
He made a new model of the Atom, with a very dense, positively charged area in the center called the NUCLEUS.
He found that the Nucleus is 100,000 times smaller than the diameter of the gold atom that he tested.

18. Rutherford’s Model
Nucleus
Electrons

20. Quick Lab
Mr. Schmidt will hand each group a small sealed box.
Write a hypothesis (educated guess) about what you think the box contains.
Carefully observe the box and its properties. Record your observations.
From your observations, draw the inside of the box. Label as many materials as possible.
How is this process similar to the process scientists have used to study the atom.

21. 1. Describe the structure of the atom according to Rutherford’s model.
Standard’s Check
1. Describe the structure of the atom according to Rutherford’s model.

22. Standard’s Check Answer
Describe the structure of the atom according to Rutherford’s model.
Rutherford’s model represents the atom as having a tiny, positively charged nucleus surrounded by mostly empty space, in which the atom’s electrons are found.

23. Bohr’s Electron Levels
In 1913, Niels Bohr, a Danish scientist who worked with Rutherford, studied the way atoms react to light.
His results led him to propose that electrons move around the nucleus in DEFINITE paths.
In his model there are no paths between the levels, but electrons can jump from one path to another.

24. The Electron Ladder
Each rung on the ladder is a definite path for the electron.
There is no path to get to the next rung.
You can stand on the rungs but not in the middle.
Electron’s must jump from one rung to another.
It takes more energy to get to the highest rung then to the one on the bottom.
Rung

25. The Modern Atomic Theory
Many 20th century scientists added to our current understanding of the atom.
Austrian physicist Erwin Shröedinger (Er veen SHROH ding uhr) and a German physicist Werner Heisenberg (Ver nuhr Hie zuhn berkh) did especially important work.
Erwin Shröedinger
Werner Heisenberg

26. The Modern Atomic Theory
They explained the nature of electrons in the atom.
They showed that electrons DO NOT travel in definite paths like Bohr suggested.
The exact path of electrons cannot be predicted.
In the current theory electrons are found in regions called electron clouds.
Sometimes the regions are called orbitals.

27. Electron Cloud Model

28. Each electron cloud consists of a certain energy level.
Energy Levels
Electron clouds are regions in an atom where electrons are likely to be found.
Each electron cloud consists of a certain energy level.
Instead of traveling in a definite path like Bohr said, each electron has a definite energy based on it’s location around the nucleus.
The energy of each electron in an atom keeps it moving around the positive nucleus to which it is attracted.

29. Bookshelf Model Each shelf is an energy level.
Each book is an electron.
You can move a book to a higher or lower shelf, but the right amount of energy must be used.
The book cannot be in between shelves.
The energy is determined by the electrons location to the nucleus

30. Electron Orbitals
Electron Orbital
Addition of Energy

31. Standards Check
1. What determines the definite energies of electrons?

32. Standards Check Answer
What determines the definite energies of electrons?
An electron’s definite energy is determined by the electron’s location around the nucleus.

33. A penny contains 2 x 1022 atoms.
The Size of an Atom
Most of what we know about the atom was discovered without seeing a single atom.
How small is an atom?
A penny contains 2 x 1022 atoms.
That is 20,000,000,000,000,000,000,000
Twenty thousand billion billion atoms of copper and zinc.

34. Summary Democritus thought that matter is made up of atoms.
Dalton based his theory on observations of how elements combine.
Thomson discovered electrons in atoms.
Rutherford discovered that atoms are almost empty with a dense, positive charged nucleus.
Bohr proposed that electrons are located at levels at certain distances from the nucleus.
The electron cloud model represents the current atomic theory of an extremely small atom.

35. Section Review
The is a particle that has a negative charge.
In your own words write a definition for the word atom.
The is where most of an atom’s mass is located.
What are the 2 main areas of an atom?

36. Section Review Answers
The electron is a particle that has a negative charge.
In your own words write a definition for the word atom.
An atom is the smallest part of an element that has the properties of that element.
The nucleus is where most of an atom’s mass is located.
What are the 2 main areas of an atom?
Nucleus and Electron Cloud.

37. The Atom
Read Pages
What you will learn:
Protons, neutrons, and electrons make up atoms.
All atoms of a given element have the same number of protons in the nucleus.
Isotopes of an element differ by the number of neutrons in the nucleus.
Atomic mass is an average of the masses of all of the naturally occurring isotopes of an element.
Four forces are at work in atoms.

38. Protons – Positive charge, located in nucleus.
The Parts of an Atom
Almost all kinds of atoms are made of the same three particles.
Protons, neutrons, and electrons are called subatomic particles because they are much smaller than the atom.
Protons – Positive charge, located in nucleus.
Electrons – Negative charge, located in electron cloud. Much smaller than protons.
Neutrons – No charge, located in nucleus.

39. Subatomic Particles Nucleus Electrons
Small, dense, positively charged center of the atom.
Protons
Positively charged particles in the nucleus of an atom.
Neutrons
Particles in the nucleus of an atom that have NO charge.
Electrons
Negatively charged particles found in electron clouds outside of nucleus.
Size of electron cloud determines size of the atom

40. Parts of an atom Complete the table below on your own. Name Location
Charge
Nucleus
Center of atom
Positive
Proton
Neutron
Electron

41. Parts of an atom Name Location Charge Nucleus Center of atom Positive
Proton
Positive (+)
Neutron
None
Electron
Electron Cloud
Negative (-)

42. The Nucleus
Only 2 kinds of particles can make up a nucleus.
Protons and Neutrons
Protons are positively charged particles of a nucleus.
Have a mass of 1.7 x g
23 zeros behind the decimal point
Since the mass is so small, scientists created the Atomic Mass Unit
1 amu = The mass of 1 proton

43. Protons and Atomic Number
The number of protons in the nucleus of an atom is the atomic number.
All atoms of an element have the same atomic number.

44. Electrons are negatively charged particles in atoms. They are:
Outside the Nucleus
Electrons are negatively charged particles in atoms.
They are:
Negatively Charged (-)
Found in Electron Cloud
Compared to protons and neutrons they have a very small mass.
Mass of 1,800 electrons = Mass of 1 proton
Usually thought of as 0.

45. Outside the Nucleus
The charge of Electron is opposite but equal to the charge of a Proton.
Charge of Electron balances out charge of Proton.
= 0
If an atom has more electrons than protons it becomes negatively charged (- charge).
Atoms can only gain or lose electrons. Every atom has a certain number of protons.

46. Copy and Complete:
Mg (Magnesium) has an atomic number of 12.
# of Protons
# of Electrons
Total Charge 12 -1 14 +2 11

47. Answers
Mg (Magnesium) has an atomic number of 12.
# of Protons
# of Electrons
Total Charge 12 13 -1 14 -2 10 +2 11 +1

48. There are over 110 elements:
Atoms and Elements
There are over 110 elements:
Protons and electrons are found in all atoms.
The simplest atom has 1 proton and 1 electron
It does not have any neutrons.
The atom is HYDROGEN.
The role of neutrons:
Since protons have a positive charge, they repel each other.
You cannot form nucleus unless you neutralize the charges

49. Hydrogen is the simplest atom. Hydrogen has 1 proton and 1 electron
Hydrogen has NO neutrons.
Hydrogen has an atomic number of 1

50. Isotopes
Isotopes are atoms of the SAME element that have the SAME number of Protons, but a different number of neutrons.
Isotopes of the same element have many properties in common
3 Isotopes of Carbon 6 6 6 C C C 12 13 14
Find how many Protons, Neutrons, and Electrons each of these Carbon Isotopes have.

51. Properties of Isotopes
Each element has only a few isotopes.
Some have special properties because they are unstable.
They are called:
Radioactive Isotopes
Radioactive atoms spontaneously fall apart after a certain amount of time.
As they fall apart they give off smaller particles and energy.

52. Standards Check
1. How do isotopes of the same element differ from one another?

53. Standards Check Answer
How do isotopes of the same element differ from one another?
Isotopes of the same element have different numbers of neutrons in the nucleus.

54. HINTS To Find: Protons: THE ATOMIC NUMBER Electrons: THE ATOMIC NUMBER
Neutrons: ATOMIC MASS – (MINUS) ATOMIC NUMBER

55. Assignment: For Atomic #’s 1-22
Element Name
Chemical Symbol
Atomic #
Atomic Mass #
# of Protons
# of
Electrons
Neutrons
Hydrogen H 1
Helium He 2
Lithium Li 3
Beryllium Be 4
Boron B 5

56. Scanning tunneling electron microscopes
Atoms
Are the smallest particles of an element that still have the element’s properties
Are described by
Are observed with
contain
Scanning tunneling electron microscopes
Modern atomic theory
Nucleus
Electron Cloud
Made of
Which consist of
At certain
Energy levels

57. Scanning tunneling electron microscopes
Atoms
Are the smallest particles of an element that still have the element’s properties
Are described by
Are observed with
contain
Scanning tunneling electron microscopes
Modern atomic theory
Nucleus
Electron Cloud
Made of
Which consist of
Protons
At certain
Energy levels
Neutrons
Electrons

58. Complete the “What I learned about atoms” portion of the KWL table.