L 11:
Models of the Atom
Models of the Atom
Which was discovered first, the proton or electron?
The electron.
What is the atomic number?
The whole number on top of the element symbol that represents the number of protons in an atom of that element.
What is an isotope?
Each of two or more forms of the same element (equal numbers of protons) that have different numbers of neutrons.
What is a nuclear reaction?
A change in the nucleus, which is not so easy to change, and is very different than a chemical reaction.
Nuclear fission involves the nucleus being split apart while nuclear fusion involves nuclei joining together to form a larger nucleus.
True or false: Each of these processes result in new elements being formed.
True - the number of protons changes in each process, so new elements will be formed.
Describe the sphere model of the atom.
The sphere model of the atom described the atom as a solid sphere that could not be divided into smaller particles or pieces.
Fill in the blanks: Atomic mass = number of ______ + ______ in an atom.
Atomic mass = number of protons + neutrons in an atom.
Explain the difference between a stable isotope and a radioactive isotope.
A stable isotope has a stable nucleus (it has a good ratio of protons to neutrons) and does not emit particles, while a radioactive isotope has an unstable nucleus and emits particles as a result of this.
What is radioactive decay?
The process of ejecting or emitting pieces from the nucleus of an atom.
What is a nuclear chain reaction?
A process that takes place when the neutrons emitted from a nucleus strike surrounding nuclei, causing them to split apart as well.
Which of the following are attracted to a negative charge (there could be more than 1): electron, proton, nucleus, neutron?
Proton & nucleus.
What does the average atomic mass represent?
The weighted average mass of all the isotopes in a naturally occurring sample of an element.
What does the diagonal line on the isotope graph represent?
Equal numbers of protons + neutrons.
Alpha decay involves the ejection of an alpha particle from the nucleus of an atom. What is an alpha particle, and what element is it?
A particle with 2 protons & 2 neutrons, which is a helium atom.
Why is it not yet possible or practical to create gold atoms through nuclear reactions here on Earth?
Nuclear reactions involve a large amount of energy and resources. Because of this, it is not possible (yet) to create enough atoms of an element for us to have a reasonable amount of that element for any benefit.
What particle(s) did J.J. Thomson include in the Plum Pudding Model?
Electrons - they were thought to be dispersed throughout positively charged fluid.
How many protons, neutrons & electrons are there in a neutral beryllium-9 atom?
In a neutral beryllium-9 atom, there are 4 protons, 5 neutrons, 4 electrons.
Using the isotope graph, would Hafnium-144 likely exist in nature? Why or why not?
No, it would not. Hafnium has 72 protons in the nucleus. Using the isotope graph, stable isotopes of hafnium have between 104 and 107 neutrons. Hafnium-144 would have 72 neutrons (144 - 72 = 72), which would not be stable according to the graph.
A nuclear decay process that involves the ejection of an electron from the nucleus of an atom, called a beta particle.
Write the nuclear equation for the alpha decay of an isotope of barium-140 to form xenon-136.
14056Ba --> 42He + 13654Xe
What is incorrect about the solar system model of the atom, which was created in 1913 by Niels Bohr?
In the solar system model of the atom, electrons circle the nucleus in specific orbits.
Why does carbon, C, have a larger atomic mass than boron, B, even though they both have 6 neutrons?
Carbon, which has an atomic number of 6, has one more proton than boron, which has an atomic number of 5.
How many protons could a stable isotope with 90 neutrons have? Which elements would these be?
Either 62, 63, or 64 protons. These elements would be Samarium, Europium, and Gadolinium.
What is the isotope name for potassium-42 after it emits an alpha particle?
Chlorine-38.
Write the nuclear equation for the beta decay of barium-140.
14056Ba --> 0-1e + 14057La