1. Atomic Structure
CHAPTER 4

2. Atoms
An atom is the smallest particle of an element that retains its identity in a chemical reaction.

3. History
Democritus ( BC): first suggested the existence of the atom

4. History John Dalton (1766-1844): proposed the Atomic Theory:
1. All elements are made of atoms
2. Atoms of the same element are identical
3. Atoms of different elements can combine to form compounds
4. Chemical reactions occur when atoms are separated, joined, or rearranged

5. Size of the atom One penny contains 2.4x1022 atoms of copper
100,000,000 atoms in a row would be 1 cm long
Atoms can be seen with special microscopes called scanning tunneling microscopes

6. Atomic Structure
An atom can be broken down into subatomic particles: protons, neutrons, and electrons.

7. Parts of an atom
The nucleus is the tiny central core of an atom containing protons and neutrons
Surrounding the nucleus is the electron field where electrons are located.

8. Protons
Protons are positively charged subatomic particles located in the nucleus

9. Neutrons
Neutrons are subatomic particles with no charge, equal in size to protons, and found in the nucleus.

10. Electrons
Electrons are negatively charged subatomic particles, which are very small, and orbit the nucleus.

11. Subatomic Particles Particle Symbol Location Charge Mass (g) Electron
orbital -
9.11 x 10-28
Proton p+
nucleus +
1.67 x 10-24
Neutron n0

12. Important Scientists
J.J. Thomson (1897) discovered electrons using a cathode ray tube.
Cathode Ray Video

13. Important Scientists
Ernest Rutherford (1911) discovered protons through his gold foil experiment.
Gold Foil Video

14. Reading and Writing in Science
1. Read pages in the red textbook
2. Answer questions 1-14 on pages 103 and 108. Write and answer these questions in your notebooks.

15. Distinguishing Among Atoms
Atoms of an element are different because they contain different numbers of protons.
The atomic number of an element is the number of protons an atom of that element has.

16. Practice How many protons does each element have? Hydrogen Carbon
Nitrogen
Potassium
Gold

17. Practice How many protons does each element have? Hydrogen = 1
Carbon = 6
Nitrogen = 7
Potassium = 19
Gold = 79

18. Mass Number
The other number on the periodic table is an atom’s mass number which is the sum of protons and neutrons.
What is the mass number of:
Hydrogen
Carbon
Nitrogen
Potassium
Gold

19. Mass Number
The other number on the periodic table is an atom’s mass number which is the sum of protons and neutrons.
What is the mass number of:
Hydrogen (1.0079)
Carbon (12.011)
Nitrogen (14.007)
Potassium (39.098)
Gold (196.97)

20. Neutrons
To determine the number of neutrons an atom has, you subtract the atomic number from the mass number, then round to the nearest whole number.
How many neutrons are found in:
Hydrogen
Carbon
Nitrogen
Potassium
Gold

21. Neutrons
To determine the number of neutrons an atom has, you subtract the atomic number from the mass number, then round to the nearest whole number.
How many neutrons are found in:
Hydrogen = 0
Carbon = 6
Nitrogen = 7
Potassium = 20
Gold = 118

22. Electrons
In a neutral atom, the number of electrons is equal to the number of protons, which is equal to the atomic number.
How many electrons does each atom have?
Hydrogen
Carbon
Nitrogen
Potassium
Gold

23. Electrons
In a neutral atom, the number of electrons is equal to the number of protons, which is equal to the atomic number.
How many electrons does each atom have?
Hydrogen = 1
Carbon = 6
Nitrogen = 7
Potassium = 19
Gold =79

24. Determining subatomic particles
Number
Protons
Atomic Number
Electrons
Neutrons
Atomic mass – atomic number

25. Isotopes
Isotopes are atoms that have the same number of protons but different numbers of neutrons (and therefore different mass numbers).

26. Isotopes The most well known isotope is Carbon-14.
Regular Carbon is called Carbon-12, because its mass number is 12, and it has 6 neutrons.
Carbon 14 has 8 neutrons (14-6).
Isotopes can be used in archeology, botany, oncology, radiology, and research.

27. Getting to know the Periodic Table
Complete the activity to help you get to know the elements of the periodic table. This is homework if you don’t finish it.
You will need to use your textbook and probably the Internet to research the periodic table and complete this activity.

28. History of Atomic Models
Over time, scientists proposed different models of atoms, each better than the last.
Thomson said it was like “plum pudding” with positive protons scattered about.
Rutherford said that positive protons were in the nucleus, and electrons orbited it.

29. Atomic Models
Bohr stated that the nucleus had positive protons, and electrons orbited in fixed shells.

30. Atomic Models
Schrodinger proposed the quantum mechanical model, which is still used today.
It states that there are protons and neutrons in the nucleus, which is surrounded by an electron cloud showing the probability of electron location.

31. Electrons
Electrons are found outside the nucleus in shells/orbitals/energy levels.

32. Energy Levels The number of electrons allowed in each energy level is:
Energy Level (n)
Maximum Number of Electrons 1 2 8 3
8 or 18 4
18 or 32

33. Placing electrons
Each energy level must be full before electrons can be placed in the next level up.
Example: Draw an atom of Lithium

34. Lithium

35. Practice
Draw an atom of Sodium.

36. Sodium

37. Practice
In your notebooks, draw the first 36 atoms. Name each one, and place the correct numbers of protons, neutrons, and electrons in each.
Next, research one way each of the 36 elements is used in real life and add it to your diagram (one sentence per element).