1. The Nucleus
Chapter 14
Section 2

2. What is an Atom? Most basic units of matter
Everything in world made up of atoms
Air you breathe
Desk you are sitting in
Your body
Smallest particle of an element with all the properties of the element that can combine with other atoms to form a molecule

3. ATOM SIZE 1 PENNY = 2X1022 Cu & Zn ATOMS
(20,000,000,000,000,000,000,000)
Thickness of aluminum foil is about 50,000 aluminum atoms stacked

4. How many different types of Atoms are there?
92 naturally occurring elements(different types of atoms
25 synthetic elements (made by scientists in laboratory)

5. Matter made of atoms of only one kind
What is an Element?
Matter made of atoms of only one kind
Example: piece of aluminum foil
Element Aluminum—many of same kind of atom
Each atom has same properties: shiny, metal, flexible

6. Most of the mass of an atom is found in the nucleus
1 amu = 1.7 X g

7. PROTONS (+)
Found In Nucleus
Positive charge
Mass = 1 amu (atomic mass unit-SI unit for measuring mass of atomic particles)

8. NEUTRONS (o)
Found In Nucleus
Neutral=no charge
Mass = 1 amu (atomic mass unit)

9. ELECTRONS(-) Found In Electron Cloud Outside The Nucleus
In a neutral Atom:
# of protons= # of electrons
The atom has no charge
Mass = almost ZERO

10. ELECTRONS(-)
Comparing the masses
1,800 electrons = 1 proton

11. Parts of the Atom Particle Charge Location Weight Proton Positive (+)
Nucleus
1 amu
Neutron
Neutral
(no charge)
Electron
Negative (-)
Electron cloud
0.018 amu
Almost zero
amu = atomic mass unit

12. Two-Dimension Model
Protons & neutrons placed together in center—nucleus
Electrons orbit nucleus in space called electron cloud
Electron cloud organized into energy levels
1st level—can hold 2 e-
2nd level—can hold 8 e-
3rd level—can hold 18 e-

13. Identifying Numbers
How does the nucleus in an atom of one element differ from the nucleus of an atom of another element?
Atoms of different elements contain different numbers of protons

14. Identifying Numbers
Atomic Number —number of protons in the nucleus of an atom
Hydrogen, smallest atom, has 1 proton
Uranium, heaviest natural atom, has 92 protons
atoms are identified by the number of protons
The number never changes without changing identity of element

15. Identifying Numbers
Isotopes –atoms of the same element that have different numbers of neutrons
element carbon has 6 protons (atomic number)
Isotopes of carbon can have 6, 7, or 8 neutrons
Mass number—number of neutrons plus the number of protons

16. Isotopes

17. Naming Isotopes CARBON-12 CARBON-14 WRITE THE NAME OF THE ELEMENT
FOLLOWED BY A HYPHEN
AND THE MASS NUMBER OF THE ISOTOPE
CARBON-12
CARBON-14

18. Isotopes of Carbon
Carbon-12
Carbon-13
Carbon-14
Mass Number 12 13 14
# protons 6
# neutrons 7 8
# electrons
Atomic Number
Average atomic mass—average mass of the mixture of an element’s isotopes

19. Isotopes of Hydrogen Example:

20. Isotopes of Hydrogen

21. Reading a Periodic Table

22. Synthetic Elements
Elements that are made in labs by smashing atomic particles into a target element
Elements with atomic numbers 93 to 112, and 114 are synthetic elements

23. Radioactive Decay The release of nuclear particles and energy.
When those nuclear particles released are protons the atomic number changes and that element changes into another element-Transmutation

24. Two protons and two neutrons
Alpha Particles
Two protons and two neutrons
Alpha particles are ejected during transmutation
Ex. Americium-241 becomes Neptunium
All atomic particles still exist just in different combinations

25. Beta Particles High-energy electron that comes from the nucleus
Electron in nucleus(aka Beta Particle) comes from a neutron that has changed to a proton and an electron
Electron(Beta Particle) is released but proton stays in the nucleus
This increases the # of protons in the nucleus and changes the element

26. Radioactive Decay
Is random-can’t tell which atoms will decay, but can predict how long it will take for half of the radioactive isotope to decay-

27. HALF-LIFE
The amount of time it takes for half of a sample of the element to decay.
Can range in length from fractions of a second to billions of years.

28. Carbon Dating
Used to determine the age of dead animals, plants(once living things-how long ago they lived)
Half-life for Carbon-14 is 5730 years
Carbon-12 makes up 99%
Carbon-13 makes up 1%
Carbon-14 makes up 1 part per million
Carbon-14 is radioactive and it is this radioactivity which is used to measure age.
knowing how many carbon-14 atoms something had before it died can only be guessed at. The assumption is that the proportion of carbon-14 in any living organism is constant.

29. Uranium-238 Used to determine the age of rocks
U-238 decays into lead 206
Half-life is 4.5 billion years
Problems- may have already been lead in rock and some isotopes may have migrated out of the rock-giving inaccurate dating

30. Uses of Radioactive Isotopes
Medical Uses: Tracer elements or radioisotopes-used to help diagnose disease
Environmental Uses:
Tracer elements watches how a plant uses a certain element(phosphorus)
In Pesticides/Fertilizers to follow the pesticide to see how it moves through an ecosystem
Water resources

31. http://www. authorstream

32. QUIZ Chapter 4, Section 2
Particle found in the nucleus that has no charge
Contains most of the mass of an atom
Negatively charged particle found outside the nucleus
Particle found in the nucleus that is positively charged

33. QUIZ Chapter 4, Section 2 The simplest atom is the __________ atom.
Particle with an unequal number of protons and electrons
SI unit used for the masses of atomic particles.
Draw and label a model of an atom. Include the three particle and their charges.

34. QUIZ Chapter 4, Section 2
Calculate the number of protons, neutrons and electrons in carbon-14.