Ch. 1—Chemistry: An Introduction What is chemistry? • Chemistry is the study of the ___________________ of substances and the changes they undergo. • It began from “_______________”... the attempts of alchemists to change common metals into _________ through trial and error. • Do you believe we can make gold? Why or why not? composition alchemy gold Half of chemistry in one sentence: “Atoms that don’t have enough electrons in the outer level will fight, barter, beg, make and break alliances, or do whatever they must to get the right number.” - Kean, Sam. The Disappearing Spoon. New York: Back Bay Publishing, 2010. Print.
composition. alchemy. Ch. 1—Chemistry: An Introduction. gold. What is chemistry? Chemistry is the study of the ___________________ of substances and the changes they undergo. - PowerPoint PPT Presentation
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Ch. 1—Chemistry: An Introduction What is chemistry?
• Chemistry is the study of the ___________________ of substances and the changes they undergo.
• It began from “_______________”... the attempts of alchemists to change common metals into _________ through trial and error.
• Do you believe we can make gold? Why or why not?
composition
alchemygold
Half of chemistry in one sentence: “Atoms that don’t have enough electrons in the outer level will fight, barter, beg, make and break
alliances, or do whatever they must to get the right number.”- Kean, Sam. The Disappearing Spoon. New York: Back Bay Publishing, 2010. Print.
How do we classify materials in chemistry?
• Elements cannot be ___________ down or _____________ into simpler substances by chemical means. Elements are the _________ forms of matter that can exists in normal laboratory conditions.
• Compounds are made up of ____ or ________ different elements ______________ bonded together. Compounds can only be broken down into simpler substances by ____________ ____________.
• Mixtures are a physical blend of two or more substances mixed together.” The parts can be separated by _____________ means or ____________ changes.
physicalphysical
broken changed
simplest
2 morechemically
chemical reactions
Chemical Symbols
• Chemists use chemical symbols for the elements involved in a chemical reaction. The symbols are a shorthand way of representing the ______________. (See the Periodic Table for a list of all the symbols.)
• The first letter of the chemical symbol for an element is always _________________.
• The next letter, if needed, is _______________. Each capital letter in a formula, therefore, represents another element.
• During chemical (or physical) reactions, mass (or matter) is neither _____________ nor _________________.
• The mass of all the reactants _________ the mass of all the products.
• The ___________ of each kind of atom is the same.
• Sometimes it appears that the reactant and product masses are not equal, but a _______ was probably a reactant or product in the reaction, and that is making the difference!
Example: 2H2 + O2 2H2O
• If 4 grams of hydrogen reacted with oxygen to produce 36 grams of water, how many grams of oxygen were used? _______
• Notice that the ____ of H’s and O’s on each side is __________!
created destroyed
equals
number
gas
32
# constant
Conservation of Mass
CaCl2 + Na2SO4 CaSO4 + 2NaCl
mass before = mass after
# atoms before = # atoms after
Atomic Theory and Structure• The smallest particle of an ________________ is an atom.
• The atom is made up of three ________________ particles.The Theory of the Atom
(1) ________________, a famous Greek teacher who lived in the 4th Century B.C., first suggested the idea of the atom.
(2) ________ __________ came up with his solid sphere atomic theory based on the results of his experiments.
(3)The proton has a ______ charge, and it was discovered in _________ by E. Goldstein.
(4)The electron was discovered in _______ by J. J. Thomson by using a cathode ray tube. The electron has a _______ charge. It’s mass is much smaller than the other 2 subatomic particles, therefore it’s mass is usually ______________.
Democritus
John Dalton
element
subatomic
1897(−)
ignored
(+)1886
Cathode Ray Tube
(4) Model:
• a ball of (+) charge containing a number of e-
• no ________________
• often described as the “________ _______________” atom.
The Nucleus• (5) Discovered by Ernest ________________ in ________.• He shot a beam of positively charged “alpha particles”,
which are ___________ nuclei, at a thin sheet of ____ ____.
•
• 99.9% of the particles went right on through to the ______________.• Some were slightly deflected. Some even ____________ ________ towards the source! • This would be like shooting a cannon ball at a piece of tissue paper and having it bounce off.
Rutherford 1911
helium gold foil
detector
bounced back
Rutherford’s Experiment
• Most of the atom is more or less _________ ___________. • The nucleus is very _________. (Stadium Analogy)• The nucleus is very _________. (Large Mass ÷ Small Volume)• The nucleus is ______________ charged.
(5) Model: • a ____________ of (+) charge surrounded by
a number of e- • no _____________ and no e- orbitals
Rutherfordnucleus
neutrons
Conclusions about the Nucleus
empty space
densetiny
positively
Nuclear Atomic Structure
• The atom is made up of 2 parts/sections:(1) The ______________ --- (in the center of the atom)(2) The ____________ _________ --- (surrounds the nucleus)
nucleuselectron cloud
(p+ & n0)
e− cloud
(6) The neutron does not have a charge. In other words, it is ________. It was discovered in ____ by James Chadwick. The neutron has about the same _________ as the proton.
• These three particles make up all the ____________________ in the Universe!
• There are other particles such as neutinos, positrons, and quarks, but are typically left for 2nd year chemistry courses.
neutral 1932mass
visible matter
Atomic Models
(7) Model:
• a nucleus of (+) charge that also contains ______________
• nucleus is encircled by e-’s located in definite orbits (or paths).
• e-’s have ___________ energies in these orbits
• e-’s do not lose energy as they orbit the nucleus
Atomic Models
Bohr
neutrons
fixed
Bohr Atomic Model
Bohr Atomic Model
How to draw your own Bohr model
• The atomic number tells you how many electrons a neutral atom will contain.
• The first energy level can only fit _____electrons (like He).
• Each energy level beyond the first one can fit ______ electrons. (or 18 if it is after the middle block which is also called the d-block)
• 2, 8, 8, 18, 18…• We will expand on this when we get to electron configurations.
• no definite ____________ to the e- path (“fuzzy” cloud)
• orbits of e-’s based on the _________________ of finding the e- in the particular orbital shape.
Quantum
shape
probability
Quantum Mechanical Model
Schroedinger's Cat
Quantum Mechanical Model(present)
Counting Subatomic Particles in an Atom• The atomic # of an element equals the number of ____________ in the nucleus. (This number is the whole number on the periodic table)
• The mass # of an element equals the sum of the _____________ and ______________ in the nucleus. (This number cannot be found on the periodic table)
• In a neutral atom, the # of protons = # of ______________. • To calculate the # of neutrons in the nucleus, ______________ the ___________ # from the __________ #.
Weighted AverageStep (1): Multiply each score by the % that it is weighted.Step (2): Add these products up, and that is the weighted average! 3.5 x .80 = 2.80 2.5 x .10 = 0.25
2.0 x .10 = 0.20 Add them up!!
A “normal average” would be calculated by simply adding the raw scores together and dividing by 3…