The Atomic Number and the Synthesis of New Elements

yoo study this shii

He was trying to figure out the

periodic table and arranged the

elements in increasing atomic

mass. However, a very small

portion of the elements known

by that time such as iodine and

tellurium does not match this

arrangement and cause a big

problem on the arrangement of

the elements.

Dmitri Ivanovich Mendeleev

He demonstrated that the atomic number determines most of the properties o fan element. This led to more accurate periodic trends across the periodic table and led to the advancements of knowledge and information on formulations of compounds.

Henry Gwyn Jeffreys Moseley

the number of protons in an atom. It alsorepresents the positive charge of the nucleus.

The atomic number (Z)

identifies the element.

Z

The symbol Z comes from the German word Zahl meaning

number

He bombarded elements with electrons and studied their X-ray spectra.

Moseley

He found that the X-ray frequency increased in a predictable way as the atomic number increased.

Moseley

He concluded that an element’s atomic number (Z) is directly related tothe charge of its nucleus and determines its position in the periodic table.

Moseley

He Published a paper showing that elements should be arranged by atomic number (Z), not atomic mass.

Moseley

Moseley found four missing elements in the periodic table, which had atomic numbers

43,61, 85, and 87.

Moseley discovery helped scientists accurately organize the periodic table and predict new elements. The method he used—bombarding elements with electrons and studying their X-ray spectra—became known as

X-ray spectroscopy.

A reaction involving the transformation of one element or isotope into another element. In 1919, Rutherford successfully carried out the first nuclear transmutation reaction.

nuclear transmutation reaction

He bombarded alpha particles (helium nuclei) from radium directed to the nitrogen nuclei. He showed that the nitrogen nucleus reacted to the alpha particle to form an oxygen nucleus.

Rutherford

a device that is used to speed up particles (e.g.protons, neutrons, alpha particles) to overcome the repulsion between theparticles and the target atomic nuclei by using magnetic and electrical fields. It is used to synthesize new elements.

particle accelerator

A compact particle accelerator that accelerates particles in a spiralpath.

cyclotron

American physicist who invented the cyclotron

Ernest Lawrence

In 1937 they discovered theelement with atomic number 43 from the radioactive parts ofLawrence’s cyclotron.

Carlo Perrier and Emilio Segrè

element with atomic number 43

Technetium (Tc)

Technetium (Tc) is after the Greek word technêtos meaning

artificial

the first man-made element.

Technetium (Tc)

In 1940, They discovered theelement with atomic number 85.

Dale Corson, Kenneth Mackenzie, and Emilio Segrè

They bombarded atoms of bismuth (Z=83)with fast moving alpha particles in a cyclotron.

Dale Corson, Kenneth Mackenzie, and Emilio Segrè

was named from the Greek word astatos meaning unstable.

astatine

Element-85

astatine

The two other elements with atomic numbers 61 and 87 were discovered through studies in radioactivity.

Element-61 (promethium) and element-87 (francium)

was discovered as a decay product of the fission of uranium

Element-61 (promethium)

was discovered as a breakdown product of actinium.

element-87 (francium)

In the 1930s, the heaviest element known with an atomic number 92 is

uranium

They proved that an element having an

atomic number 93 could be created. They

used a particle accelerator to bombard

uranium with neutrons and created an

element with an atomic number 93 which

they named neptunium

Edwin McMillan and Philip Abelson

an atomic number 93 which they named

neptunium.

1940, element-94 was synthesized. They bombarded uranium with deuterons(particles composed of a proton and a neutron) in a cyclotron. Element-94 wasnamed plutonium.

Glenn Seaborg, Edwin McMillan, JosephKennedy, and Arthur Wahl.

Elements with atomic numbers greater than 92 (the atomic number of uranium) are called

Transuranium elements

neptunium and plutonium are both transuranium elements. they decay radioactively into other elements. All transuranium elements are artificially generated or synthetic elements. They are prepared using nuclear reactors or particle accelerators.

They are unstable