Flashcards for Chapter 4 in Chemistry

What is Dalton’s atomic theory?
States that matter is composed of extremely small particles called atoms; atoms are invisible and indestructable; atoms of a given element are identical in size, mass, and chemical properties; atoms of a specificelement are different from those of another element; different atoms combine in simple whole-number ratios to form compounds; in a chemical reation, atoms are separated, combined, or rearranged
What is an atom?
the smallest particle of an element that retains all the properties of that element; is electrically neutral, spherically shaped, and composed of electrons, protons, and neutrons
What is the atomic mass unit (amu)?
one-twelfth the mass of a carbon-12 atom
What is atomic mass?
the weighted average mass of the isotopes of the element-the mass of the protons and neutrons in an element
What is atomic number?
the number of protons in an atom
What are isotopes?
atoms of the same elemnt with differnt numbers of neutrons
What is the mass number?
the number after an element’s name that represents the sum of the protons and neutrons
What is an alpha particle?
a particle with two protons and two neutrons, with a 2+ charge; is equivalent to a helium-4 nucleus, is emitted during radioactive decay
What is alpha radiation?
radiation that is made up of alpha particles; is deflected toward a negatively charged plate when radiation from a radioactive source is directed between two electrically charged plates
What is a beta particle?
a high-speed electron with a 1- charge that is emitted during radioactive decay
What is beta radiation?
radiation that is made up of beta particles; is deflected toward a postively charged plate when ratiation from a radioactive source is directed between two electrically charged plates
What is a gamma ray?
high energy radiation that has no electrical charge and no mass, is not deflected by electric or magnetic fields, usually accompanies alpha and beta radiation and accounts for most of t he energy lost during radioactive decay
What is a nuclear equation?
a type of equation that shows the atomic number and mass number of the particles involved
What is a nuclear reaction?
a reaction that involves a change in the nucleus of an atom
What is radiation?
the rays and particles-alpha and beta particles and gamma rays-that are emitted by radioactive materials
What is radioactive decay?
a spontaneous process in which unstable nuclei lose energy by emitting radiation
What is radioactivity?
the process in which some substances spontaneously emit radiation
What is an anode?
the positive region in a cathode ray
What is a cathode?
the negative region in a cathode ray
What is a cathode ray?
radiation that originates from the cathode and travels to the anode of a cathode-ray tube
What were Democritus’ views on matter and the atom?
matter is composed of atoms that move through empty space; atoms are solid, homogeneous, indestructible, and indivisible; different kinds of atoms have different sizes and shapes; size, shape, and movement of atoms determine the properties of matter
What were Aristotle’s ideas about matter?
empty space cannot exist and matter is made of earth, fire, air, and water
What was J.J. Thomson’s model?
the plum pudding model
What was Rutherford’s experiment/model?
the one where he shot an alpha particle through the sheet of gold. some bounced back and others went through. this showed that atoms had dense nuclei; Rutherford also said that the atom had protons
What was Chadwick’s discovery?
he developed the neutron
What is the mass of a proton?
1 amu
What is the mass of a neutron?
1 amu
What is the mass of an electron?
1/1840 amu
How are atomic mass and mass number the same? different?
Atomic mass and mass number have the same numerical value, but atomic mass has a unit
When adding an alpha particle, what do you do?
subtract 4 from the mass number and 2 from the atomic number
When adding a beta particle, what do you do?
add one to the atomic number, but the mass number remains the same
Where is a beta particle from?
the desintigration of a neutron
Why does a gamma ray have no mass?
because it isnt a particle
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