Evolution of Atomic Theory [Part II]

2

No. of neutrons in the α particle

Ernest Marsden

Ernest Rutherford’s colleague

Geiger counter

The first portable device that detects and measures radiations.

Hans Geiger

German physicist who invented the Geiger counter

Luminescent

(Adjective) emitting light that is not caused by heat

Nucleus

A small, relatively heavy, and positively charged body, that is at the center of each atom.

79

Atomic number of gold

118

Number of neutrons in a gold atom

The positively charged subatomic particle found in the nucleus.

Named by Ernest Rutherford

While naming it he stated that the nuclei of other elements contain the hydrogen nucleus as a “building block”

Radioactive ores

Types of rocks or minerals that naturally contain radioactive elements, like uranium, thorium, or radium.

Mesothorium

Name give to a so-called “new element” produced by the radioactive decay of thorium in 1907

Isotopes

Atoms of the same element but with a different atomic mass

Frederick Soddy

An English chemist who was awarded the Nobel Prize in Chemistry in 1921 for his discovery of Isotopes

1932

Year when the evidence of neutrons were discovered

James Chadwick

An English physicist who found the evidence of neutrons

Neutron

An uncharged, subatomic particles with a mass approximately same as that of proton