hi students it's been a long time welcome back to my strong techie youtube channel another video lesson about grade 9 science quarter 2. quarter 2 is about chemistry interesting right week one last one is all about the quantum mechanical model in this video i will show to you the history of how atoms are developed throughout the years here are our learning objectives identify the development of history of atom give the importance of the development of atom in today's generation at the end of this video you are going to describe how bohr model of the atom improved luther ford's atomic model so please keep on watching and join me to the history of atoms [Music] before we start let us have a very short game called jumble i will be showing pictures and try to arrange the jumbled letters to form award so without further ado let's start this game first word what can you say about this word this is matter that is right anything that has mass and occupy space is called matter let us have the second one this is atom it is the smallest unit of matter and the building blocks of matter that is atom next what is this word this is protons these are the positively charged particle how about the fourth one this word is electrons that is right these are the negatively charged particles let us have the last one this is neutrons that is correct these are the uncharged neither positive nor negative they were discovered by james chadwick in 1932 so that's it class you did awesome did you refresh some of your stock knowledge about chemistry alright now let us continue now let us have some trivia here is eugene goldstein he discovered the idea about the positively charged particle called proton amazing right now let us proceed to the history of atomic beauty let us start history of atoms again atom is the smallest particle of an element the smallest amount of a substance that can take part in any chemical reaction let us have the first person who began to search for a description of matter and he is democratus he named the smallest piece of matter called atomos meaning not to be cut and this is his atomic model they were small hard particles that were all made of the same material but for different shapes and sizes this piece is indivisible so take a look of his atomic model next next is john dalton in the early 1800s john dalton an english chemist performed a number of experiments that eventually led to the acceptance of the idea of atoms he deduced that all elements are composed of atoms and this is his atomic model as you can see atoms of the same element are exactly alike according to him atoms of different elements are different compounds are formed by the joining of atoms of two or more elements so this is john dalton's atomic model next joseph john thompson in 1897 j.j thomson an english scientist provided the first hint that an atom is made of even smaller particles additional information he introduced the idea about the negatively charged particle called electrons his model is also known as the plum pudding atomic model according to him atoms were made from positively charged substance with negatively charged electrons scattered about like raisins in a pudding that is why it is also known as the plum coding atomic model next let us have ernest rutherford in 1908 ernest rutherford an english physicist was handed work on an experiment he reasoned that all atoms are positively charged particles were contained in the nucleus as you can see all the protons were contained in the nucleus while the electrons were scattered they were all scattered outside the nucleus around the atom's edge so this is the ernest rutherford atomic model next niels bohr in 1913 niels bohr a danish scientist proposed an improvement [Music] and this is his atomic model he plays each electron in an specific energy level electrons move in definite orbits around the nucleus much like planet circles the sun or our solar system this orbits or energy levels are located at the certain distances from the nucleus so this is his atomic model now let us proceed to arnold sommerfeld he is a brilliant physicist modified niels bohr's atomic fury to include elliptical orbits this is arnold sommerfeld's atomic model according to him electrons are moving around the nucleus assumed that orbits doesn't have to be spherical but can also be elliptical and this is the most popular image of atom nowadays and the last one he is irwin scrodinger he is a physicist and a biologist and was considered the father of quantum mechanics today's atomic model is based on the principles of wave mechanics according to him electrons do not move around an atom in a definite path like the planets around the sun take a look of his atomic model according to him a space in which electrons are likely to be found electrons whirl about the nucleus billions of times in one second they are not moving around in random patterns location of electrons depends upon how much energy the electron has and that is how atoms were developed and evolved throughout the use i hope you learned something new today about the history of atoms thank you so much for watching do not forget to like share and subscribe bye [Music]