Chemistry Unit 3
What is the symbol for carbon-12
12 C 6 ^
Beta decay of 14 C 6 ^
14 C = 14 N + 0 e 6 ^ 7 ^ -1 ^
The half-life of Co-60 is 5.3 years. How much of a 1.000 mg sample of Co-60 is left after a 15.9 year period?
15.9/5.3 = 3 half-lifes 1.000, 0.5000, 0.250, 0.125
What is the atomic mass of chlorine with 18 neutrons? How does this compare to the mass of chlorine on the periodic table?
18 + 17 = 35 35, 35.45
Alpha decay of 238 U 92 ^
238 U = 234 Th + 4 He 92 ^ 90 ^ 2
How many electrons in molybdenum-96?
42
How many neutrons in 59 Co? 27 ^
59 - 27 = 32
If you have 6 neutrons and 6 protons what is the charge of the nucleus?
6+
Electron
a particle with a negative charge; move very fast around the outside of the nucleus of atoms
Proton
a particle with a positive charge, found in the nucleus of atoms
Nuclear Reaction
a process that involves changes to the nucleus of an atom
Chain reaction
a series of fission reactions
Model
a simplified representation of something more complex that facilitates understanding certain aspects of a real object or process
Radioactive decay
a spontaneous process by which an atom emits radiation or a particle from its nucleus of an atom
Amu is based on the (blank) atom.
carbon-12
If you change the number of (blank) in an atom you also change the elemental identity of that atom.
protons
How to find atomic mass?
protons + neutrons
Atomic theory
states that all matter is made of atoms
Nucleus
the dense, positively charged structure found in the center of the atom; it is composed of protons and neutrons
Fusion
the joining of two nuclei to form a larger nuclei accompanied by a release of energy
Atomic number
the number of protons in the nucleus of an atom of an element; in the periodic table, the elements are arranged in order by atomic number
Natural percent abundance
the percentage of each isotope of an element that occurs in nature
The diagonal line on the isotope graph represents nuclei with
the same number of protons as nuetrons
Atom
the smallest unit of an element that retains the chemical properties of that element
Fission
the splitting apart of an atomic nucleus into two smaller nuclei accompanied by a release of energy
Nuclear chemistry
the study of changes to the nucleus
Mass number
the sum of the numbers of protons and neutrons in the atom
Half-life
the time required for one half of the radioactive atoms in a sample to decay
Neutron
a particle that does not have a charge, found in the nucleus of atoms
Isotopes
atoms of the same element that have different numbers of neutrons
Average atomic mass equation
average atomic mass = total mass/number of atoms
Explain why the mass number of an atom does not change when a beta particle is emitted.
b/c only an electron is lost which has almost no atomic mass
Explain why the mass of an atom changes when an alpha particle is emitted.
b/c the atom loses two protons and two neutrons
An alpha particle is not a neutral atom. It has a charge of +2. Why is this the case.
b/c there are no electons
The isotopes of the elements after (blank) (atomic number (blank) and up) are all radioactive.
bismuth, 84
If an atom has equal numbers of protons, neutrons, and electrons, what is the charge of the atom?
0
How many protons in fluorine-23?
9
Calculate the atomic mass of neon: Neon-20: 10 neutrons, 90 atoms Neon-22: 12 neutrons, 9 atoms Neon-21: 11 neutrons, 1 atoms
90(20) + 9(22) + 1(21)/100 = 20.19
Beta decay
A nuclear reaction in which a neutron changes into a proton, and the atom emits a beta particle; the atom's atomic number increases by 1
What type of radiation is most harmful to living things?
Gamma radiation because it can penetrate several inches of lead before stopping.
Is an atom with a nucleus of 31 protons and 31 neutrons a stable isotope?
No because the larger the element, the more neutrons it needs in order to remain stable.
Would an atom with 60 protons and a mass number of 155 be stable?
No because there would be too many neutrons causing it to disintegrate.
Nuclear vs Chemical Reaction
Nuclear changes the nucleus. Chemical has the same elements
Describe how elements are formed in nature.
Supernovas
Daughter isotope
The resulting isotope in a nuclear reaction
Parent isotope
The starting isotope in a nuclear reaction
Alpha decay
a nuclear reaction in which an atom emits an alpha particle; its atomic number decreases by two and its mass number decreases by 4
Alpha particle
a particle composed of two protons and two neutrons, equivalent to the nucleus of a helium atom
Gamma ray
a form of high-energy electromagnetic radiation emitted during nuclear reactions
An isotope of iron, Fe, has 26 protons and 32 neutrons. What is the approximate mass of the isotope (a) and how would you write the symbol for the isotope (b)?
a: 26 + 32 = 58 amu b: 58 Fe 26 ^
What is the average atomic mass (a), atomic number (b), and most abundant isotope (c) of phosphorus, P?
a: 30.97 b: 15 c: phosphorus-31
a: 10 B b: 5 ^
a: mass number b: atomic number
Beta particle
an electron emitted from the nucleus of an atom during beta decay
Radioactive isotope
any isotope that has an unstable nucleus and decays over time
How to find neutrons?
atomic mass - protons
Strong nuclear force
force that holds together the subatomic particles of the nucleus; keeps atoms stable
Describe the different processes that might result in a change in atomic identity.
fusion, fission, alpha decay, and beta decay
In general, elements with an even atomic number
have more isotopes than those with an odd atomic number
