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Chemistry ch. 3+21

The Atom and Nuclear Chemistry

QuestionAnswer
Formula of Density: Mass/volume
Dalton's Atomic Theory (5 pts) Elements are made up of atoms. Atoms of the same element are equal. Atoms of diff. elements can join to = molecules. Reactions occur when atoms are separated, joined or rearranged. Atoms of 1 type can't be changed to a diff. 1 UNLESS radioactive isotope.
Ion Atom with either a + or - charge (lost or gained electrons).
Cation A positively charged ion.
Anion A negatively charged ion.
Isotopes Atoms of the same element with different masses, because they have the same # of protons and electrons, but a diff. # of neutrons.
% abundance The % of each isotope found in a sample/in nature.
Chemical Reaction The transformation of substances into one or more new substances.
The Law of Conservation of Mass Mass is neither created or destroyed.
Modern Atomic Theory (5 pts) All matter is composted of atoms. Atoms of 1 element differ due to # of neutrons (& ions vary in electrons). Atoms of 1 element combine w/ others to=compounds (not always in = proportions). Atoms can be destroyed in nuclear chain reactions.
Atom the smallest particle of an element that retains that element's chemical properties.
Subatomic Particles Protons, neutrons, electrons. They show that atoms are divisible.
How was the electron discovered? Cathode Ray Tube testing
Electrons have a _____ charge to mass ratio. The charge is___ and the mass is ___ Large. Negative, zero
Where are electrons located in the atom? The electron cloud
What is the electron's purpose? Makes an Ion (gains/loses an electron), it gives an atom it's physical and chemical properties, chemical bonding.
Who discovered the nucleus and what did they conclude? Rutheford, that atoms are mostly empty space.
What does the nucleus consist of? Densely packed positive matter including protons and neutrons.
What determines an atom's identity and why? Protons, because each nucleus has a different # of protons.
What is the mass and charge of a proton? Mass= 1 amu, charge = positive.
Where is the neutron located and what is its function? Neutrons are in the nucleus, they hold the nucleus together and are responsible for different isotopes.
What is the mass and charge of a neutron? Mass=1amu, charge=neutral
Nuclear Forces short range proton-neutron, proton-proton, neutron-neutron forces holding the nuclear particles together.
Atomic Radius the distance from the center of the nucleus to the outer portion of the electron cloud.
what is the mass number? The sum of the protons+neutrons of each atom of an element.
What is the atomic number? The number of protons in an atom of an element.
Nuclide an isotope identified by the number of protons and neutrons in its nucleus
How are isotopes identified? By mass number (neutrons+protons)
How do most elements naturally occur? As mixtures of isotopes.
What is an Atomic Mass Unit? 1/2 the mass of a carbon-12 atom
What is the Average Atomic Mass? the weighted average of the atomic masses of the isotopes of an element.
How is the Average Atomic Mass calculated? By multiplying the atomic ass of each isotope by its relative abundance (in decimal form) and adding the results.
What can we now know using the relative atomic mass scale? How many atoms of an element are present in a sample.
Mole the amount of a substance that contains as many particles as there are atoms of carbon in 12g of Carbon-12. (a mole is a counting unit)
Avogadro's # the number of particles in one Mole of a pure substance. 6.022x10^23
What is the formula for Avogadro's Number? Number of particles= (# of moles)x(Avogadro's #)
Molar Mass The mass of one mole of a pure substance measured in g/mole
What is the molar mass numerically equal to? The atomic mass of the element.
To get the mass when given the # of moles of a substance, what is the formula? (# of moles)x(molar mass)=Mass
To get the Volume of gas when given the # of moles of a substance, what is the formula? (# of moles)x(22.4 L/mol)= Volume of gas
To get the number of particles when given the # of moles of a substance, what is the formula? (# of moles)x(Avogadro's #)= # of particles (molecules, atoms, FUs)
Democritus discovered atoms
JJ Thompson Discovered electrons through the plumb pudding model.
Nucleons Protons and Neutrons (what the nucleus consists of)
Mass Defect The difference between the mass of an atom and the sum of its subatomic particles which is caused by the conversion of mass to energy at the formation of the nucleus.
Nuclear Binding energy the energy released when a nucleus is formed from Nucleons, this is the energy required to hold the nucleus together and is used to measure the stability of the nucleus.
The Binding energy of the Nucleus is used for comparing the stability of different nuclides.
In the Nuclear Shell Model, the ____ the binding energy of the nucleus, the ____ stable the nuclide is. higher, more.
A band of stability is graphed Neutron to proton ratios of stable nuclides.
Which neutron to proton ration is most stable? 1:1
Magic Numbers the most stable nuclides have 2,8,20,28,50,52,or 126 protons, neutrons or total nucleons. Magic numbers represent completed nuclear energy levels.
Nuclear Reaction A reaction that changes the nucleus of an atom.
Why and how does a Nuclear Reaction occur? Nuclear reactions happen in unstable nuclei and it changes the # of protons and/or neutrons to increase stability.
Transmutation A change in the identity of a nucleus due to a change in its protons.
Radioactive Decay the spontaneous disintegration of a nucleus into a lighter nucleus with the byproduct of emitted particles, electromagnetic radiation or both.
A Radioactive Nuclide Has an unstable nucleus that undergoes radioactive decay.
Nuclear Radiation: Alpha Decay/Emission emits an a-particle to decrease the # of neutrons and protons to increase stability.
What is an a-particle? 2 protons and 2 neutrons; 2(top)4(bottom)He(base)
Nuclear Radiation: Beta Decay/Emission To decrease the # of neutrons, a neutron is converted into a proton and an electron; the electron is emitted as a Beta particle.
What is a B-particle? an electron emitted from a nucleus; 0(top)-1(bottom)e or B(base)
Nuclear Radiation: Gamma Emission a change in the nuclear energy levels (nuclear shell model) from an excited state to a ground energy state. (Gamma rays almost always emitted with a particle)
What is a Y-Ray? a high-energy electromagnetic wave emitted during a change in energy levels; 0 mass 0 charge
Nuclear Radiation: Positron Emission When a proton is converted into a neutron to decrease the number of protons it emits a positron.
Nuclear Radiation: Electron Capture An inner orbital electron is captured by the nucleus of the same atom.
What is a Positron? when a proton is converted into a neutron, a positron is emitted. Same mass as an electron, but a positive charge; 0(top)+1(bottom)e or B(base)
What is an Electron 0(top)-1(bottom)e(base)
Nuclear Radiation: Neutron Emissions are seen during fission and fusion neutron emissions are the loss of neutrons.
What is a neutron? 0 charge, 1 amu; 1(top) 0(bottom) n(base)
(Radioactive Dating) 1/2 Life (t1/2) The time required for half the atoms of a radioactive nuclide to decay.
More stable nuclides decay _____ and have ______ half lives. Slower, longer.
Radioactive Dating The process by which the age of an object is determined based on the amount of certain radioactive nuclides.
How is age estimated with radioactive dating? Age is estimated by measuring either the accumulation of a daughter nuclide or the disappearance of the parent nuclide.
Radioactive Traces radioactive atoms incorporated into substances so that the substance can be followed by radiation detectors.
Fission when an unstable nucleus (heavy) splits into 2 or more lighter, stable nuclei. Missing mass is converted to energy.
What mass is most stable? Intermediate mass
When does Fission occur? spontaneously or when bombarded by particles.
Critical Mass Enough radioactive nuclides to sustain Nuclear reactions.
Fusion Very high temperature and pressures are used to combine light nuclei to make a heavy, more stable nucleus.
What are the differences between Fission and Fusion? Fusion creates more energy. The byproducts of Fusion are not radioactive. Fusion needs the temperature of the sun to begin.
Chain Reaction a reaction in which the material catalyst is also a product of the reaction and can start another reaction.
Nuclear Reactors use controlled-fission chain reactions to produce energy and radioactive nuclides.
Nuclear Reactors: Control rods Block the path of some neutrons, keeping the system from reaching supercritical mass.
Nuclear Reactors: Moderator Slows down the fast neutrons produced by fission.
Nuclear Radiation can cause ionization of atoms/molecules that have been affected by energy transferred by nuclear decay.
rem Measures the does of any ionizing radiation in people.
Background Radiation radiation from everything in the universe that organisms are subject to daily.
What are 3 devices that detect radiation? Film Badges, Scintillation counters, and Geiger-Muller counters.
Created by: Agardengirl