Title: Chem Review 2 TOPIC: DISCOVERY OF ATOM EQ: How were the 3 subatomic particles discovered?
Title and Highlight Topic: EQ: Date Reflect Question: Reflect on the material by asking a question (its not suppose to be answered from notes) NOTES: Write out the notes from my website. Use different types of note-taking methods to help you recall info (different color pens/highlighters, bullets, etc) When I lecture we will add more info, so leave spaces in your notes DRAW ANY PICTURES, FIGURES, AND WRITE OUT ANY PRACTICE PROBLEMS/QUESTIONS. WE WILL ANSWER THEM TOGETHER. So LEAVE SPACES SO WE CAN ANSWER QUES. Summary (end of notes) : 1-2 Sentences of what you learned
ATOMS AND ELEMENTS ATOM - Building Blocks of Matter An atom is the smallest particle of an element that retains the chemical properties of that element. An element is a substance that cannot be broken down into simpler substances. There are about 91 different elements in nature, and consequently about 91 different kinds of atoms. (The other 27 are synthetic man made elements)
Draw THE ATOM - TIMELINE Dalton (1803) Atomic Theory Rutherford (1911) Gold Foil Experiment Proton & Nucleus (Mass and Volume) Democristus 400BC Aristotle 4 elements Thomson (1897) Plum Pudding Model Cathode Ray Tube electrons Millikan (1909) Charge & Mass of electron Chadwick (1932) Neutron
(1) Most of the atom is more or less empty. space (2) The nucleus is very tiny and. dense (3) The nucleus is positively charged due to protons. (4) The nucleus (protons and neutrons) is 99.97% of an atom s mass. (5) The electron cloud = majority of volume SO. atoms is neutral: the positive (nucleus) balances out the negative electrons So, why do electrons stay surrounded around the nucleus? Opposites attract
A SUMMARY OF THE NATURE OF ELECTRICAL CHARGE Positive and negative electrical charges attract each other. Positive positive and negative negative charges repel each other. Positive and negative charges cancel each other so that a proton and an electron, when paired, are chargeneutral. Draw this with notes in color!!!
Rutherford s Model of the Atom Draw this with notes!!! 2.2
THE STRUCTURE OF THE ATOM The atom is composed of two main regions: the nucleus & the electron cloud.
The atom is made up of three subatomic particles. THE ATOM Draw this with notes in color!!!
NUCLEUS OF AN ATOM Nucleus- VERY small region located at the center of the atom. The nucleus accounts for most of an atoms mass but very little volume, making it a very dense region. The nucleus contains protons & neutrons. proton = p + neutron = n o
ELECTRON CLOUD OF AN ATOM The electron cloud is the negatively charged region of the atom that accounts for most of the atom s volume but very little of the atom s mass. The electron cloud is composed of electrons. electron = e -
Draw SUBATOMIC PARTICLES Particle Symbol Location Electrical charge Mass (amu) Actual Mass (g) Electron e - Outside nucleus Proton p + Nucleus +1 1-1 1/1840 9.11x10-28 (About 2000 times smaller than Proton and neutron) 1.67x10-24 Neutron n 0 nucleus 0 1 1.67x10-24 They have the SAME Mass
PRACTICE PROBLEMS #1 What are the two main regions of the atom? What is the charge on the nucleus?
CHEMICAL SYMBOLS Chemists use chemical symbols to represent elements. The chemical symbol consists of 1 or 2 letters. The first letter ALWAYS. capitalized The next letter is. lowercase
THE PERIODIC TABLE OF THE ELEMENTS LISTS ALL KNOWN ELEMENTS ACCORDING TO THEIR ATOMIC NUMBERS. Draw BOX
The # of protons in the nucleus of an atom that identifies an element. The # of protons in the nucleus of an atom is its atomic number.
The Mass Number (A), (rounded to the nearest integer) Mass# = p + + n o # of neutrons = mass number # p + Atomic number (Z). Protons determines the identity of the element. A# = p + = e - (atoms are neutral) A is always the larger number than Z.
LOOK FOR THE ELEMENT CHLORINE.. LET S WRITE HIS CHEMICAL SYMBOL NOTATION
MASS NUMBER ATOMIC NUMBER Symbol notation # PROTONS + # NEUTRONS 35 Cl 17 NUMBER OF PROTONS
LOOK FOR THE ELEMENT CARBON.. LET S WRITE HIS CHEMICAL SYMBOL NOTATION
SYMBOL NOTATION Element followed by a hyphen mass# Carbon-12
Difference between Mass and Atomic weight Atomic weight is the weight of all the isotopes for that element (decimal #) Mass number is the rounded number for the atomic weight. Example: Copper Atomic weight 63.546 Mass number - 64
Make chart Left side Element Atomic # Mass # Oxygen - 8 Mass number -31 31 15 Sodium - 23 PRACTICE PROBLEMS p + n o e - Symbol 33 42 91 140 Uranium - 238 26 80 35 Br
4.8 ISOTOPES: WHEN THE NUMBER OF NEUTRONS VARIES All atoms of an element have the same # of protons. They do not have the same # of neutrons. Atoms with the same # of protons but different # of neutrons are called isotopes. Example Hydrogen
ISOTOPES
EXAMPLE OF AN ISOTOPE ATOMIC MASS 35 Cl 37 Cl 17 17 18 NEUTRONS 20 NEUTRONS ATOMIC NUMBER
Review. How to write Symbol Notation
Left side Practice Problem #2 Circle which of the following are isotopes. 40 X 40 X 42 X 40 X 43 X 20 18 20 19 20
Left side Practice Problem #3 Determine the number of protons, neutrons and electrons in the neutral (non-charged) isotopes of the following atoms: 88 38 Sr 84 38 Sr
The atomic masses listed in the Periodic Table are a weighted average of all the isotopes of the element. Units = atomic mass unit (amu)
All elements have their own unique percent natural abundance of isotopes. Naturally occurring chlorine consists of 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). Which isotope is the most abundant?