The Atom, Isotopes, Radioactivity, and Nuclear Processes

Flashcards cover atomic structure, isotopes, radioactive decay, nuclear reactions (fission and fusion), and key figures in atomic theory. Fill in the blank style to practice core concepts.

The atomic number is the number of __.

protons

The mass number is the total number of __ in the nucleus (protons + neutrons).

protons and neutrons

Isotopes are atoms of the same element that have different numbers of __.

neutrons

Atomic mass is the weighted average mass of all __ of an element.

isotopes

In isotope notation A/Z X, A is the mass number and Z is the __.

atomic number

If an atom gains electrons, it becomes a negatively charged ion called an __.

anion

If an atom loses electrons, it becomes a positively charged ion called a __.

cation

The process by which unstable nuclei emit particles and transform into a stable nucleus is called __.

radioactive decay

Alpha decay emits an __ particle, which is a helium nucleus containing 2 protons and 2 neutrons.

alpha

An alpha particle is equivalent to a(n) __.

helium nucleus

In beta decay, a neutron is turned into a proton and a __ is emitted.

beta particle (electron)

Positron emission occurs when a proton is turned into a neutron and a __ is emitted.

positron

Ra-226 decays to Rn-222 via __ emission.

alpha particle

Nuclear fission is the splitting of a large nucleus into __ nuclei.

smaller

To sustain a chain reaction you must have a large enough quantity of 235U close together for the emitted neutrons to collide with the __ nuclei.

235U

In fusion, two small nuclei __ to form a larger nucleus.

combine

Fusion releases more energy per mass than fission; the Sun releases energy primarily through __.

fusion

Dalton's Atomic Theory states that atoms are __ and combine in simple whole-number ratios to form compounds.

indivisible

Dalton's theory also states that atoms of a given element are __ to one another.

identical

Atoms of different elements combine in simple whole-number ratios to form __.

compounds

A chemical reaction involves the rearrangement, separation, or __ of atoms.

combination

Democritus, around 400 BCE, first proposed the idea of the __.

atom

Isotopes are atoms of the same element that have a different number of __.

neutrons

The nucleus contains protons and neutrons; electrons reside in the surrounding __.

electron cloud (or orbitals)

Most of the volume of an atom is __ space.

empty

Thomson's Plum Pudding Model described electrons embedded in a positively charged __.

sphere

Millikan calculated the electron's charge and estimated its mass to be about __ kg.

9.11 x 10^-31

Rutherford's gold foil experiment showed the nucleus is a very small, dense __.

nucleus

Chadwick discovered the __ located in the nucleus.

neutron

In Bohr's model, electrons occupy defined __ around the nucleus.

energy levels

When an electron falls from a higher energy level to a lower one, the emitted photon has a wavelength that becomes __ as the energy difference increases.

shorter

Be bombardment produced radiation that behaved like protons but had no charge; these particles were __.

neutrons