Ch. 2 - Atoms, Isotopes, and Nuclear Chemistry Flashcards
Who developed the law of conservation of mass?
Antione Lavoisier in 1785
What is the law of conservation of mass?
Matter cannot be created of destroyed. The mass of the products equals the mass of the reactants.
Who developed the law of constant composition (aka the law of definite proportions)?
Joseph Proust in 1794
What is the law of constant composition?
The proportions of the elements in a given chemical compound are fixed.
Who developed the modern atomic theory?
John Dalton in 1808
What is the modern atomic theory?
- All matter consists of solid and indivisible atoms..
- Atoms are indestructible and retain their identity in all chemical reactions..
- All of the atoms of a given chemical element are identical in mass and in all other properties..
- Different elements have different kinds of atoms;; these atoms differ in mass from element to element..
- Compounds consist of elements combined in small whole - number ratios..
What is the mass number?
The Mass number (A) is the number of nucleons. It is written on the top left of an element’s symbol.
What are nucleons?
Protons and neutrons.
What is an atomic number?
An atomic number (Z) is the number of protons. Is is written on the bottom left of the element’s symbol.
What are isotopes?
Atoms of the same atomic number with differen’t mass numbers.
What is the formula to find the average mass of an element from its isotope masses?
Mav = Σ(% abundance of isotope/100%) x Misotope
What is the formula to calculate % abundance?
% abundance = (# of atoms of isotope / total # of atoms of element) x 100%
What is the symbol for a proton?
11p
What is the symbol for a neutron?
10n
What is the symbol for a beta particle (an electron)?
1-1ß
What is the symbol for a positron?
11ß
What is the symbol for an alpha particle?
42a or 42He2+
What are the seven nuclear reactions?
- Alpha emission
- Beta emission
- Positron emission
- Electron capture
- Fission
- Fusion
- Bombardment
What are the reactants and products of an alpha emission? Is it spontaneous?
1 nucleus produces 1 nucleus and 1 alpha particle spontaneously.
What are the reactants and products of a beta emission? Is it spontaneous?
1 nucleus produces 1 nucleus and 1 electron spontaneously.
What are the reactants and products of a positron emission? Is it spontaneous?
1 nucleus produces 1 nucleus and 1 positron spontaneously.
What are the reactants and products of an electron capture? Is it spontaneous?
1 nucleus and 1 electron produce 1 nucleus spontaneously.
What are the reactants and products of fission? Is it spontaneous?
1 nucleus produces 2 nuclei and some neutrons non-spontaneously.
What are the reactants and products of fusion? Is it spontaneous?
2 light nuclei produce 1 nucleus and some neutrons either spontaneously or non-spontaneously.
What are the reactants and products of bombardment? Is it spontaneous?
2 heavy nuclei produce 1 nucleus and some neutrons non-spontaneously.
What are properties of alpha radiation?
Alpha particles are bigger than other forms of radiation and have a +2 charge so it is easliy stoped but can be highly damaging if ingested.
What are properties of beta radiation?
Beta particles have a -1 charge and have a stronger penetrating power than alpha radiation that can cause radiation burns and other biological damage.
What are properties of gamma radiation?
Gamma radiation is high energy electromagnetic radiation. It has no mass and no charge so it passes right through matter and causes serious biological damage.
What are neutrinos?
They are particles with a neutral charge and and a small mass that creates weak interactions with matter. They carry most of the energy generated in many nuclear reactions.
What is the absorbed dose?
A measure of the amount of radiation abrosbed by a given mass of tissue. Measured in grays (Gy) where 1 Gy = 1 J/kg.
What is the euqivalent dose?
A measure of how much biological damage can be done by the radiation absorbed. (The absorbed dose is multiplied by a radiation weighting factor (WR) to calculate the dose in gamma rays). It is measured in sieverts (Sv) where 1 Sv = 1 J/kg.
If Z = 1-20, what is the ideal N to Z ratio?
N = Z
If Z = 20-82, what is the ideal N to Z ratio?
N > Z, up to N = about 1.5 Z
If Z is 83+, what is the ideal N to Z ratio?
No stable nuclides exist.
What reaction does neuclear binding energy measure?
When individual protons and neutrons come together to make a nucleus.
What is the formula to find nuclear binding energy?
ΔE = Δmc2 = (mnuclide - mnucleons) x c2
What is the formula to find nuclear binding energy per nucleon?
Eb = ΔE / A, where A is the mass number
As Eb increases, do nuclides become more or less stable?
More stable.
What is activity?
Activity (A) is the quantity of atoms decaying over a given time period.
What is a Geiger counter?
A device that uses a tube of gas to click when radiation is present and ionizes the gas in the tube.
What formula describes how the number of radioactive atoms decreases over time?
N2 = N1e-k Δt, where N = number of radioactive atoms and can be replaced by activity (A)
OR
ln(A2) = ln(A1) -k Δt
What is the formula to find half-life?
ln(N2/N1) = -k Δt
