Chem #1 Test Review

What is an isotope?

Atoms of the same element with different numbers of neutrons.

What is average atomic mass?

The weighted average mass of an element's naturally occurring isotopes.

How do you calculate average atomic mass?

Multiply each isotope's mass by its decimal abundance, then add the results.

How do you convert a percent to a decimal?

Divide the percent by 100. Example: 34.6% = 0.346.

What is an alpha particle?

A particle containing 2 protons and 2 neutrons; mass number 4 and atomic number 2.

What happens during alpha decay?

Mass number decreases by 4; atomic number decreases by 2.

What happens during beta-minus decay?

Mass number stays the same; atomic number increases by 1.

What is a beta particle?

A high-speed electron released from the nucleus during beta-minus decay.

What happens during gamma decay?

Energy is released; mass number and atomic number stay the same.

What is nuclear fusion?

Two smaller nuclei join to form a larger nucleus.

What is nuclear fission?

A large nucleus splits into smaller nuclei, usually releasing neutrons and energy.

What must be balanced in a nuclear equation?

The total mass numbers and total atomic numbers on both sides.

What is the mass number?

The total number of protons and neutrons in the nucleus.

What is the atomic number?

The number of protons in the nucleus.

How do you find the number of neutrons?

Subtract atomic number from mass number.

How do you identify an element?

Use its atomic number, which equals its number of protons.

What is half-life?

The time it takes for half of a radioactive sample to decay.

How much remains after one half-life?

One-half, or 50%, of the original sample.

How much remains after two half-lives?

One-fourth, or 25%, of the original sample.

How much remains after three half-lives?

One-eighth, or 12.5%, of the original sample.

How do you calculate the number of half-lives?

Divide total elapsed time by the length of one half-life.

How do you calculate remaining mass after each half-life?

Divide the remaining mass by 2 for each half-life.

How is an isotope symbol written?

Mass number goes at the upper left of the element symbol; atomic number goes at the lower left.

How many electrons does a neutral atom have?

The same number of electrons as protons.

How do you find the missing particle in a nuclear equation?

Balance the total mass numbers and atomic numbers on both sides.