Nuclear Chemistry, Atoms: The Building Blocks of Matter

The change in the identity of an isotope due to a change in the number of its protons

When an isotope loses a particle with a 2 proton and a mass of 4

When an isotope gains a proton through the loss of an electric charge on one of its neutrons

When an isotope decays to release only energy, not a particle

a positive particle with the same mass as an electron given off as a result of a proton changing to a neutron

the amount of time it takes for half of a substance to decay into another substance

a negative sub atomic particle

the splitting of one large nucleus to create two smaller nuclei (two new elements with some mass being converted into energy)

the combining of two smaller nuclei to create a larger nucleus (some mass is converted to energy)

the process using Carbon-14 to date materials that were once alive

a charged atom

an atom with fewer or more neutrons than the average form of that element

“indivisible” (Greek meaning), the smallest particle of an element that retains the chemical properties of that element

All matter is made of atoms and atoms are indivisible, cannot be subdivided, created or destroyed

All atoms of the same elements are identical in mass and properties (the same)

Compounds are combinations in whole number ratios of two or more types of atoms

In chemical reactions, atoms are combined, separated or rearranged

Compounds are made in definite proportions

(Law of Lavoisier) in chemical reactions, the total mass is conserved

(Proust) when a chemical compound is formed, their is a definite proportion of the atoms forming the compound (example: in table salt; sodium chloride; it ALWAYS has by mass, the same amount of sodium (Na , 39.34%) and chlorine (Cl, 60.66%)

if 2 or more different compounds are composed of the same 2 elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ration of small whole numbers. (carbon and oxygen form carbon dioxide and carbon monoxide; the ratio of carbon to oxygen between dioxide to monoxide is always 2:1)

number of protons of each atom of that element

atoms of the same element that have different numbers of neutrons in the nucleus (so different atomic masses)
Tin has the most isotopes (10); although they differ in masses isotopes do not differ significantly in their chemical behavior

the total number of protons plus neutrons that make up nucleus of an isotope

general term for a specific isotope of an element

(amu) a unit of mass that describes the mass of an atom or molecule

(mol) the SI unit for amount of substance:
the amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12

the number of particles in exactly one mole of a pure substance

(6.022 1415 x 10^23 or rounded to 6.022 x 10^23 = exactly what 12g of carbon-12 atoms contains)

equal to the atomic mass of the element; the mass of one mole of a pure substance is called the molar mass of that substance; written in units of g/mol; FOUND ON THE PERIODIC TABLE FOR EACH ELEMENT

what make up an atom; the three main are protons,neutrons, and electrons

transformation of a substance or substances into one or more new substances

a very small region located at the center of an atom

positively charged (+) particle equal in magnitude to the negative charge of an electron; at least one in every atom

neutral particle; at least one or two in every atom

negative charged particle (-); surrounds the nucleus in an occupied region

glass tubes; in late 1800s, experiments were performed where electric current was passed through various gases at low temp; the resulting glowing stream was called cathode rays

weighted average of the atomic masses of the naturally occurring isotopes of an element

(1897) discovered electrons, charge to mass ratio and that all cathode rays are composed of identical negatively charged particles named electrons

(1911) discovered the nucleus, protons;
Gold foil experiment

(1934) discovered the neutrons

the short-range proton-neutron, proton-proton, and neutron-neutron forces hold the nuclear particles together

Mass # – atomic # = # neutrons
(protons+neutrons)-protons=neutrons

streams of negatively charged particles (electrons).

JJ Thomson; negative electrons are spread evenly through the positive charge of the rest of the atom (think watermelon)

1. since atoms are electronically neutral they must contain a positive charge to balance the negative electrons
2. because electrons have so much less mass than atoms, atoms must contain other particles that account for most of their mass

bombarded a thin piece of gold foil with a narrow beam of alpha particle, some particles were deflected back to source – reasoned this was the nucleus and it was a very small part of atom because the rest of the particles passed through undisturbed

different elements differ in number of protons (positive charge) so the number of protons determines the atoms identity

the short range proton-neutron; proton-proton and neutron-neutron forces that hold the nuclear particles together

Radius of an atom from the center of the nucleus to the outer portion of the electron cloud ;
1 pm = 10^-12(ten to the negative 12th power) meters or 10^-10 centimeters

number of protons in each atom of that element

Identified by specifying their mass number in 2 ways:
1. Hyphen notation: hydrogen – 3
2. Nuclear symbol: 3
H
1
with mass number (neutron + protons) on top and atomic number (protons) on bottom

all atoms compared to carbon-12 atoms (12 amu) so 1 amu = 1/12 of carbon

multiply mass of each type by the decimal fraction representing its % in the mixture

25% = .25 each weighing 2g;
75%=.75 each weighing 3g so

(2g*.25)+(3gx.75)=2.75g

(moles of substance) x molar mass = grams and
(moles)(gram/moles)=grams

1911 model of the atom. small nucleus surrounded by electrons in orbit around it

Suggest that electrons move in a definite path around the nucleus. 1913

a mathematical model and most accurate model of an atom used today

The first major model of the atom, developed in 1800.

Basically, this model was a philosophical idea that everything could be broken down into one fundamental unit — the atom. It could not be tested at that point in time because the Greeks did not posses the technology to observe anything that was so microscopic such as the atom.

the protons and neutrons in atomic nuclei

the reference to an atom in nuclear chemistry; identified by the number of protons and neutrons in its nucleus

difference between the mass of an atom and the sum of the masses of its protons, neutrons and electrons

conversion of mass to energy upon formation of the nucleus

the energy release when a nucleus is formed from nucleons; E=mc^2

is the binding energy per of the nucleus divided by the number of nucleons it contains – the higher the binding energy the more tightly the nucleons are held together and are therefore more stable

stable nuclei cluster over a range of neutron-proton ratios (the graph of elements and their isotopes plotted)

nucleons exist in different energy levels or shells in the nucleus

Numbers of nucleons that represent completed nuclear energy levels: 2, 8, 20, 28, 50, 82, and 126 – the most stable nuclides

reaction that affects the nucleus of an atom

change in the identity of a nucleus as a result of a change in the number of its protons

the spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles, electromagnetic radiation or both

1896 wrapped a photographic plate in lightproof covering and place uranium on top of it. Figured out didn’t need sunlight to expose the plate, it was the radioactive decay of uranium that exposed the plate

particles or electromagnetic radiation emitted from the nucleus during radioactive decay

an unstable nucleus that undergoes radioactive decay – all nuclides beyond atomic #83 are unstable and radioactive

two protons and two neutrons bound together and emitted from the nucleus during some kinds of radioactive decay; charge is 2+, represented by symbol

an electron emitted from the nucleus during some kinds of ratioactive decay. atomic number 1+, mass stays the same

particle that has the same mass as an electron but has a postive charege, and is emitted from the nucleus during some kinds of ratio active decay

an inner orbital electron is captured by the nucleus of its own atom. the inner orbital electron combines with a proton and a neutron is formed; atomic number decreases by one but mass number doesn’t change (stays the same)

high energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground energy state

alpha: your hand
beta: aluminum
gamma: lead
neutrons: concrete

time required for half of the atoms of a radioactive nuclide to decay

a series of ratioactive nuclides produced by successive radioactive decay until a stable nuclide is reached

heaviest nuclide of each decay series

nuclides produced by the decay of the parent nuclides

radioactive nuclides not found naturally on earth

bombardment of nuclei with charged and uncharged particles to make artificial radioactive nuclides; radioactive isotopes of all the natural elements have been produced this way

elements with more than 92 protons in their nuclei – all are radioactive

unit used to measure nuclear radiation exposure

unit used to measure the dose of any type of ionizing radiation that factors in the effect that the radiation has on human tissue

use exposure of film to measure the approximate radiation exposure of people working with radiation

are instruments that detect radiation by counting electric pulses carried by gas ionized by radiation; typically used to detect beta particles, x rays and gamma radiation

instruments that convert scintillating light to an electrical signal for detecting radiation

process by which the approximate age of an object is determined based on the amount of certain radioactive nuclides present: Carbon 14 is radioactive has half life of approximately 5715 years can be used to estimate the age of organic material to about 50,000 years

radioactive atoms that are incorporated into substances so that movement of the substances can be followed by radiation detectors – used to diagnose cancer etc

nucleus of very heavy atom (uranium) split into 2 or more lighter nuclei; releases high amounts of energy

reaction in which the material that starts the reaction is also one of the products and can start another reaction

minimum amount of nuclide that provides the number of neutrons needed to sustain a chain reaction

use controlled fission chain reactions to produce energy and radioactive nuclides

use energy as heat from nuclear reactors to produce electrical energy

radiation absorbing material that is used to decrease exposure to radiation especially gamma rays from nuclear reactors

neutron absorbing rods that help control the reaction by limiting the number of free neutrons

used to slow down the fast neutrons produced by fission

low mass nuclei combine to form a heavier more stable nucleus; opposite of fission; creates even more energy; cannot currently be controlled due to heat; named and explained by Lise Meitner