hello seniors it's been a while and i'm glad to see you all again another journey is yet to overcome let's step ahead in learning another exciting area of science that's concerned with the study of inanimate natural objects including physics chemistry astronomy and related subjects students it's time to learn physical science my lesson today the atomic number and the synthesis of new elements at the end of this lesson you should be able to explain how the concept of atomic number led to the synthesis of new elements in the laboratory identify the different elements formed after the process of synthesis and realize the importance of the atomic number in identifying the new element's identity in the periodic table our first stop mostly x-ray spectroscopy henry green jefferies mostly was an english physicist who demonstrated that atomic number or the number of protons in an atom determines most of the properties of an element he began his study of radioactivity in earnest eduardo for its laboratory but later decided to explore more on x-rays in 1913 mostly published a paper and arrangement of the elements in the periodic table based on the atomic numbers he used x-ray spectroscopy to determine the atomic number of an element he bombarded a beam of electrons to different elements and measured their x-ray spectral lines his results clearly showed that frequency of the x-rays given off by an element was mathematically related to the position of that element in the periodic table the frequency is proportional to the charge of the nucleus or the atomic number when the elements were arranged according to their atomic numbers there were four gups in the table this gaps corresponded to the atomic numbers 43 61 85 and 87 these elements were later synthesized in the laboratory through nuclear transmutations let's move on to the discovery of nuclear transmutation in 1919 ernest ruder ford successfully carried out a nuclear transmutation reaction a reaction involving the transformation of one element or isotope into another element he bombarded alpha particles from regime directed to the nitrogen nuclei he showed that the nitrogen nuclei reacted the alpha particles to form an oxygen nuclei the reaction is written as shown in the slide however both alpha particles and atomic nuclei are positively charged so they tend to repel each other therefore instead of using fast moving alpha particles in synthesizing new elements atomic nuclear often bombarded with neutrons or neutral particles in particle accelerators next is the discovery of the missing elements recall that in 1925 there were four vacancies in the periodic table corresponding to the atomic numbers 43 61 85 and 87. two of these elements were synthesized in the laboratory using particle accelerators a particle accelerator is a device that is used to speed up the protons to overcome the repulsion between the protons in the target atomic nuclei by using magnetic and electrical fields it is used to synthesize new elements in 1937 american physicist ernest lawrence synthesized element with atomic number 43 using a linear particle accelerator he bombarded molybdenum with atomic number 42 with fast moving neutrons the newly synthesized element was named technician or tc after the greek word tecnatus meaning artificial tissue was the first man-made element in the year 1940 dale carson kenneth ross mckenzie and emilio segre discovered element with atomic number 85 then bombarded atoms of bismuth with atomic number 83 with fast moving alpha particles in a cyclotron a cyclotron is a particle accelerator that uses alternating electric field to accelerate particles that move in a spiral path in the presence of a magnetic field element 85 was named astatine from the greek word estatus meaning unstable the two other elements with atomic number 6 to 1 and 87 were discovered through studies in radioactivity element 61 or the prometheum was discovered as a decay product of the fiction of uranium while element 87 a franchise was discovered as a breakdown product of uranu moving on synthesis of new elements in the 1930s the heaviest element known was uranu with atomic number 92. early in 1940 edwin mcmillan proved that an element having an atomic number 93 could be created he used a particle accelerator to bombard uranium with neutrons and created an element with an atomic number 93 which he named neptunium at the end of 1940 element 94 was synthesized by seaboy macmillan kennedy and wall they bombarded uranium with deuterons or particles composed of a proton and the neutron in cyclotron element 94 was named plutonium elements with atomic numbers greater than 92 or atomic number of uranium are called transuranium elements hence neptunium and plutonium are both transuranium elements they are unstable and decay radioactively into other elements all of these elements were discovered in the laboratory as artificially generated synthetic elements they are prepared using nuclear reactors or particle accelerators next is nuclear transmutation a nuclear transmutation is a reaction involving the transformation of one element into another element it happens when a nucleus reacts with a subatomic particle to produce a more massive nucleus the course only on special conditions such as the collision of the target nuclei with a beam of particles with high energies in 1919 the first successful transmutation was done by ruder foid he bombarded nitrogen nuclei with alpha particles to form oxygen nuclei in the next decades other nuclear reactions were discovered by bombarding other elements with alpha particles however since these particles have a strong repulsive force with the target nuclei because both are positively charged the progress in discovering elements was slow scientists then tried other particles with higher energies in 1932 major advancements and nuclear reactions took place particle accelerators which use a projectile of high energy particles were invented trans-uranium elements assad earlier transuranium elements are elements whose atomic numbers are greater than 92 or the atomic number of uranium they are all unstable and undergo radioactive decay many of the transuranium elements were prepared using particle accelerators and much of this work was facilitated by a group of scientists led by the american chemist glen theodore seborg and later nuclear scientist albert giorso in the university of california the most effective way of preparing trans-uranium elements specifically in the lower members of the series elements 93-95 was through nitrogen bombardment as for the heavier transuranium elements or from 96 to 101 they were generally prepared with high energy positive ions which include the use of deodorants carbon nuclei and ions the first transuranium element was identified by edwin macmillan and philip abelson in 1940 it was named neptunium bearing an atomic number of 93. they acquired the rage active isotope of neptunium through the bombardment of uranium oxide with slow neutrons this reaction can be represented as shown in the slide after the discovery of neptunium the decay of this element led to the discovery of another element bearing an atomic number of 94. seaborg together with macmillan wall and kennedy bombarded uranium with deuterons to form neptunium-238 with a half-life of two days which then decayed into plutonium with a half-life of 92 days the reactions can be represented as shown nuclear decay reaction nuclear dk reaction also known as radioactive decay is a reaction in which the nucleus emits radiation and transforms into a new nucleus the parent nuclei are unstable and the resulting daughter in nuclear are more stable having lower mass and energy transuranium elements are unstable that they undergo radioactive decay resulting in more stable elements the nuclear decay reactions involved in the synthesis of transuranium elements are alpha decay beta decay and spontaneous fission the alpha decay is a reaction that emits helium-4 nucleus or alpha particle this decay produces a daughter nucleus with an atomic number reduced by 2 and a mass number reduced by 4 compared with the parent nucleus most nuclei with mass numbers greater than 200 undergo this type of decay the general reaction can be represented as follows and as shown in the slide where a is the mass number z is atomic number x represents the parent nucleus and y represents a dotted nucleus again atomic number is reduced by two and the mass number is reduced by four for example neptunium neptunium-237 the most abundant isotope of the neum undergoes alpha decay to form protactinium-233 the nuclear reaction is represented as shown at the left side of the equation is the mass and atomic numbers of netonium as it undergoes alpha decay it will then become protactinium with mass number of 233 and atomic number of nine to one 233 is the resulting number when 4 is subtracted from 237 and 91 is from 93 minus 2. you may refer to the periodic table of elements as your reference in beta decay a neutron is converted into a proton and emits an electron in the form of a beta particle the atomic number goes up by 1 while its mass number remains the same the general reaction can be represented as shown again the atomic number goes up by 1 while its mass number remains the same for example curium 249 undergoes decay by beta particle emission to form by killium 249. the balance equation for this reaction is represented as shown and as revealed the mass number remains the same to 49 and because we added 1 to 96 97 is the resulting number in spontaneous fashion the nucleus breaks into pieces into different atomic numbers and mass numbers this occurs in very massive nuclei for instance californium 254 undergoes spontaneous fission making value set sufficient products one possible set can be represented as shown remember in nuclear reactions the parent nucleus is on the left side of the equation the daughter nucleus and the emitted particle are on the right side and the number of nuclei is always conserved let's sum up our learnings today the atomic number is the number of protons which is positively charged particles in an atom henry green jeffries mostly was an english physicist who demonstrated the atomic number or the number of protons in an atom determines most of the properties of an element in 1919 ernest lutherford successfully carried out a nuclear transmutation reaction or a process of transforming one element or isotope into another element in 1925 there were four vacancies in the periodic table corresponding to the atomic numbers 43 61 85 and 87. elements with atomic numbers 43 and 85 were synthesized using particle accelerators a particle accelerator is a device that is used to speed up the protons to overcome the repulsion between the protons and the target atomic nuclei by using magnetic and electrical fields it is used to synthesize new elements elements with atomic numbers greater than 92 or atomic number of uranium are called trans-uranium elements they were discovered in the laboratory using nuclear reactors or particle accelerators nuclear reaction is the process where two nuclei collide to produce new ones there are two types of nuclear reaction nuclear transmittation and nuclear decay reaction nuclear transmutation is a reaction involving the transformation of one element or isotope into another element this process occurs only in special conditions such as the collision of target nuclei with the beam of particles with high energies transuranium elements are elements whose atomic numbers are greater than 92 they are all unstable and undergo radioactive decay high energy positive ions which include the use of deodorants carbon nuclei and ions are used for synthesizing massive nuclei nuclear dk reaction is a reaction in which the nucleus of an element emits radiation and transforms into another nucleus the nuclear decay reactions involved in the synthesis of transuranium elements are alpha decay beta decay and spontaneous fission alpha decay produces daughter nucleus with an atomic number reduced by 2 the mass number reduced by 4 compared with the parent nucleus in beta decay the atomic number of the nucleus increases by 1 while its mass number remains the same and in spontaneous fission cerebral fission products are produced from the parent nucleus the sum of the mass numbers is equal to the mass number of the parent nucleus similarly the sum of the atomic numbers is equal to the atomic number of the parent nucleus that's the end of our lesson today it's been my pleasure teaching you one of the amazing topics of physical science and i really hope you learned something from this video lesson thank you and may god bless us all let's meet again in our next video