Unit 3 CHEM study guide

Isotope

Atoms of the same element with different numbers of neutrons

Gold foil experiment

-expected alpha particles to go straight through foil -some were deflected -determined deflections were from positive charges being centralised in a dense region -discovered the nucleus -only Center is positive

Strong nuclear force

A force that acts on subatomic particles that are extremely close together

Beta particle

A high-speed electron with a 1- charge that is emitted during radioactive decay

Electron

A negatively charged, fast-moving particle with an extremely small mass that is found in all forms of matter and moves through the empty space surrounding an atoms nucleus

Neutron

A neutral, subatomic particle in an atoms nucleus that has a mass nearly equal to that of a proton

Alpha particle

A particle with two protons and two neutrons, with 2+ charge; is equivalent to a helium-4 nucleus, can be represented by a; and is emitted during radioactive decay

Nuclear reaction

A reaction that involves a change in the nucleus of an atom

Radioactive decay

A spontaneous process in which unstable nuclei lose energy by emitting raditation

Proton

A subatomic particle in an atoms nucleus that has a positive charge of 1+

Nuclear equation

A type of equation that shows the atomic number and mass number of the particles involved

What change in mass number occurs when a radioactive atom emits an alpha particle? A beta particle? A gamma particle?

Alpha (α) decay. When an alpha particle is emitted from a nucleus the nucleus loses two protons and two neutrons. This means the atomic mass number decreases by 4 and the atomic number decreases by 2.

Describe what happens to unstable nuclei.

Alpha (α), beta (β-) and gamma (γ) decay. When the nucleus of an atom possesses either too many or too few neutrons compared to the number of protons it becomes unstable. These are called radioactive isotopes. Unstable nuclei split up in a process called radioactive decay and emit radioactive radiation.

Describe the structure of a typical atom. Identify where each subatomic particle is located.

An atom consists of three sub-atomic particles; protons, neutrons, and electrons. The protons and neutrons are located in the nucleus of the atom. Electrons are found in clouds surrounding the nucleus.

Billard Ball model

Because Dalton thought atoms were the smallest particles of matter, he envisioned them as solid, hard spheres, like billiard (pool) balls, so he used wooden balls to model them

Cathode ray tube/plum pudding model

Cathode tubes are pressurised with gas; when electrified, gas glows -rays of light->deflected by charged plates -electrons=positive

Compare nuclear fission and nuclear fusion reactions. Describe the particles that are involved in each type of reaction and the changes they undergo.

Different types of reactions that release energy due to the presence of high-powered atomic bonds between particles found within a nucleus. In fission, an atom is split into two or more smaller, lighter atoms. Fusion, in contrast, occurs when two or more smaller atoms fuse together, creating a larger, heavier atom.

Atomic theory (who discovered it, what was discovered, why was it important)

Discovered by: Democritus What was discovered: proposed the idea that matter was not infinitely divisible Important because: he believed matter was made up of tiny individual particles called atoms. He believed that atoms could not be created. Destroyed, or further divided

Modern atom theory

Electrons do not travel in orbits, it is used to calculate the probability of finding an electron in a given location

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 the energy lost during radioactive decay

What quantities are conserved when balancing a nuclear reaction?

In both nuclear and chemical reactions, two physical quantities are seen to be conserved and unchanging: the number of particles and the total charge.

Explain how the existence of isotopes is related to the fact that atomic masses are not whole numbers.

Isotopes are atoms with different numbers of neutrons in the nucleus. Neutrons are a little bit heavier than protons, so when you add a neutron, you add a little bit more than 1 amu.

Atomic mass unit

One-twelfth the mass of a carbon 12-atom

Alpha radiation

Radiation that is made up of alpha particles; is deflected toward a negativtely charged plate when radiation from a radioactive source is directed between two electrically charged plates

Beta radiation

Radiation that is made up of beta particles; is deflected toward a positively charged plate when radiation from a radioactive source is directed between two electrically charged plates

How do unstable atoms gain stability?

Radioactive decay-is the process by which the nucleus of an unstable atom loses energy by emitting radiation, including alpha particles, beta particles, gamma rays, and conversion electrons.

Radioactivity

The process in which some substances spontaneously emit radiation

How can you determine the number of neutrons in an atom if it's mass number and it's atomic number are known?

Take the atomic mass which you can get off the periodic table and subtract the atomic number (# of protons) from it. So if you have Titanium (TI) which has a mass of 47.90 amu and you know the # protons (atomic #) of 22 : 47.9-22 to find the neutrons = 26 (round).

Penetration power

The ability of radiation to pass through matter

Transmutation

The conversion of an atom of one element to an atom of another element

Does the existence of isotopes contradict part of Dalton's original atomic theory? Explain.

The existence of isotopes contradicts part of Dalton's original atomic theory because he said all atoms of a given element are identical have the same mass size and chemical properties.

Nucleus

The extremely small, positively charged, dense Center of an atom that contains positively charged protons and neutral neutrons

How is the mass number related to the number of protons and neutrons an atom has?

The mass number is the total number of protons and neutrons in an atoms nucleus. The number of protons is the same as the elements mass number minus the atomic number

Critical mass

The minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction

Mass number

The number after an element's name, representing the sum of its proteins and neutrons

Atomic number

The number of protons in an atom

Necleon

The positively charged protons and neutral neutrons contained in an atoms nucleus

Radiochemical dating

The process that is used to determine the age of an object by measuring the amount of a certain radioisotope remaining in that object

Radiation

The rays and particles-alpha and beta particles and gamma rays-that are emitted by radioactive materials

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

Nuclear fission

The splitting of a nucleus into smaller, more stable fragments, accompanied by a large release of energy

Nuclear fusion

The splitting of a nucleus into smaller, more stable fragments, accompanied by a large release of energy

What particles are found in the nucleus of an atom? What is the charge of the nucleus?

The subatomic particles of protons and neutrons are found in the nucleus of an atom. Electrons, which have a negative charge, are particles that can found orbiting outside the nucleus of an atom.

Half-life

The time required for one-half of a radioisotopes nuclei to decay into its products

Atomic mass

The weighted average mass of the isotopes of that element

How many protons and electrons are contained in an atom of element 44?

There are 44 electrons and 44 protons. The number of protons is the atomic number. The number of electrons on an atom is also the atomic number.

Which subatomic particle identifies an atom as that of a particular element?

There are 8 electrons total. If there are 8 electrons, then there are 8 protons. Eight protons means the atomic number is 8

Compare and contrast Thomson's plum pudding atomic model with rutherfords nuclear atomic model

Thompson's didn't have a nucleus, and Rutherford's did. Also, Thompson's had electrons surrounding the positive charge, while Rutherford has them in rings around the nucleus.

What is the primary factor that determines whether a nucleus is stable or unstable?

balance of protons and neutrons in a nucleus

How do isotopes of a given element differ? How are they similar?

differ: from each other in their mass numbers and the number of neutrons they contain. similar: All of the isotopes of an element, however, contain the same number of protons, which is equal to that element's atomic number.

Explain how it is possible that fission (the splitting of nuclei) and fusion (the combining of nuclei) both release tremendous amounts of energy.

how tightly the protons and neutrons are held together. If a nuclear reaction produces nuclei that are more tightly bound than the originals then energy will be produced, if not you will need to put energy in to make the reaction happen.

Electron orbital

is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus.

What type of reaction involves changes in the nucleus of an atom?

nuclear reactions

describe the current limitations of fusion as a power source

our inability to contain the fusion reaction in a manner that requires less energy than the amount of energy which can be extracted

Compare the relative charge and mass of each of the subatomic particles

proton: positive charge; 1- mass: 9.11x10-28 electron: negatively charged; 1+ mass: 1.674x10-24 neutron: neutral; 0 mass: 1.675x10-24

How is an atom atomic number related to its number of protons? To it's a number of electrons?

the atomic number is the number of protons in an atom and if it's a neutral atom then it is also the number of electrons

Describes the forces acting on the particles within a nucleus and explain why neutrons are the glue holding the nucleus together.

the nucleus of an atom is held together by the strong force, while the electrons are held in the atom by the electric force.

An isotope of mercury has 80 protons and 120 neutrons. What is the mass number of this isotope?

the sum of the neutrons and protons is the mass number (A) in this problem, the answer for mass number of mercury isotope is: 80 protons +120 neutrons=200