Chemistry Unit 3

Normal chemical reactions involve an atom's outer electrons, but nuclear chemistry involves changes to the __________ and __________.

protons and neutrons

Changing the number of protons in an atom’s nucleus creates

a completly different element (transmutation)

What do we call atoms of the same element that have different numbers of neutrons?

isotopes

 Why do nuclei undergo radioactive decay?

they are trying to reach a stable configuration

 A Half-life is the time it takes for exactly __________ of a radioactive sample to decay.

half

 If you have 100g of a substance, how much is left after two half-lives have passed?

25g

Beta-particle Emission

atomic number increases by 1 and the mass number remains the same

alpha particle emission

atomic number decreases by 2 and the mass number decreases by 4

positron emission

atomic number decreases by 1 and the mass number remains the same

electron capture (k-capture)

atomic number decreases by 1 and the mass number remains the same

What is the difference between a chemical reaction and a nuclear reaction?

Chemical reactions involve changes in electron configurations and the formation of new chemical bonds, while nuclear reactions involve changes within the atomic nucleus, potentially transforming elements

Define radioactivity

the spontaneous decay of unstable atomic nuclei, accompanied by the emission of radiation

Describe what happens when a nucleus is stablilized by converting a proton into a neutron

a proton transforms into a neutron, decreasing the atomic numberby one while the mass number remains the same

Describe what happens when a nucleus is stablilized by emitting an alpha particle

the nucleus loses an alpha particle, decreasing its atomic number by 2 and its mass number by 4

Explain how a beta emission results in an increase in the atomic number by one, but no increase in the mass number

a neutron converts into a proton and an electron, the elctron is emitted, increasing the atomic number by one, while the toal number of nucleons remains constant, meaning the mass number does not change

There are 264 stable isotopes of the approximately 1500 known isotopes. If the stable isotopes where plotted on a

graph according to number of protons vs number of neutrons, it would form a pattern called the ________________

________________________________.

band of stability

Decay will occur in such a way as to return an unstable __________________ to the band of stability.

nucleus

Above element number 20, the most stable nuclei contain a number of neutrons that is _________________ than

the number of protons.

greater

Above element #83, all isotopes are _____________________________ and ________________________________.

radioactive and unstable

Which type of radiation can be stopped by a sheet of paper? ____________________________________________.

alpha radiation