Atomic Structure | Grade 8 Science DepEd MELC Quarter 3 Module 3

[Music] hi there did you know that the entire universe is made up of matter and energy all matter is made up of elements that cannot be broken down by chemical activity atoms are the building blocks of everything in this universe including ourselves the atom is the smallest unit of an element that can exist either alone or in combination with atoms of the same or different elements it is the smallest unit of matter that retains the identity of a substance a molecule can be defined as the combination of two or more atoms which are held together by chemical bonds a molecule is the smallest portion of a substance which showcases all the properties of the substance greek philosophers leucopus and democritus proposed earliest concept that a smallest particle of matter is an atom that is indivisible coined the term atomus to describe the indivisibility of an atom john dalton proposed the atomic theory of matter in 1803. he pictured the atom as a solid indestructible sphere with a mass like a billiard ball dalton's atomic theory states that matter is made up of very small invisible and indivisible particles called atoms atoms of the same element have the same properties atoms of different elements differ in properties atoms cannot be created nor destroyed in any chemical reaction atoms combine with each other in whole number ratios to produce compounds dalton's atomic theory gave explanations to the fundamental laws in chemistry these are the law of conservation of mass the law of definite proportion and the law of multiple proportions the cathode ray experiments in 1897 a various scientists including joseph john thompson led to the discovery of the electron thompson proposed a plump pudding model he found that atoms could sometimes eject a far smaller negative particle which he called an electron his discovery showed that atoms were not indivisible but composed of subatomic particles that are electrically charged he believed that an atom is a big positive sphere where negatively charged electrons are scattered throughout in 1911 ernest rutherford discovered the nucleus of the atom using his alpha scattering experiment he and his colleagues tested thompson's theory using a very thin sheet of gold foil [Music] they focused on a stream of alpha particles and they discovered that most of the particles passed through and few were deflected or scattered at a wide angle some were deflected at very large angles and there were some that bounced back to the source after rutherford's discovery james chadwick found a neutral particle with no net electrical charge inside the nucleus and called this particle the neutron niels bohr proposed an atomic model similar to the solar system where electrons are found revolving around the nucleus electrons are found in specific energy levels where they can move from one energy level to another by absorbing or releasing energy an austrian physicist irvin schrodinger made a refinement of war's atomic model he used mathematical equations to describe the possibility of finding an electron in a certain location this model of the atom made use of electron clouds as probable position of the electrons imagine an electric fan with its blades spinning at high speeds this was how the surface of the electrons may appear this model is known as the quantum mechanical model of the atom advance ideas of the modern atom include the following electrons of atoms are found in specific quantized energy levels electrons are not stationary but continuously move outside the atomic nucleus electrons occupy specific atomic orbitals atoms are composed of two regions the nucleus is the center of the atom that contains the mass of the atom this is where protons and neutrons are located the electron cloud is the region that surrounds the nucleus that contains most of the space in the atom a typical atom consists of three subatomic particles protons neutrons and electrons the electron is the lightest of all the three subatomic particles it carries a net charge of negative one and is represented by the symbol e with a negative superscript it is located outside the nucleus a proton carries one positive charge and is represented by the symbol p with a positive superscript it is located inside a nucleus the neutron has no net electrical charges it is represented by the symbol n with a zero superscript it is located inside the nucleus the atomic number and mass number of an element are given in the periodic table of elements the mass number is the atomic weight or atomic mass rounded off to a whole number the mass of an atom is influenced by the mass of the nucleus thus the mass number is equal to the mass of protons and neutrons the atomic mass is measured in atomic mass units the atomic number is the number of protons of an element it can be used to identify the atom an element is a neutral atom therefore an element has an equal number of protons and electrons the following formulas will help you remember how to get the number of subatomic particles of an element atomic number equals number of electrons equals number of protons mass number equals number of protons plus number of neutrons number of neutrons equals mass number minus number of protons where the capital z is the atomic number the capital a is for the mass number e with a negative superscript is for the number of electrons p with a positive superscript is for the number of protons and n with a zero superscript is for the number of neutrons to get the mass number round off the atomic mass to the nearest whole number for helium the mass number is 4 atomic mass units to get the number of protons and electrons remember the formula atomic number equals number of electrons equals number of protons thus helium has two electrons and two protons to get the number of neutrons get the difference between the mass number and number of protons to get helium's number of neutrons we subtract 4 which is the mass number to 2 which is the number of protons therefore helium has 2 neutrons let's try solving for the number of protons number of electrons and number of neutrons in a particular atom how many protons electrons and neutrons are there in a sodium atom the symbol of sodium designates an atom that has a mass number of 23 and an atomic number of eleven the number of protons in an atom of sodium is eleven the number of electrons is also equal to eleven the number of neutrons in the nucleus is equal to the mass number minus the number of protons or 23 minus 11 which is 12. an atom is electrically neutral it has neither a positive or a negative charge in order for an atom to be neutral the number of electrons must equal the number of protons atoms however can sometimes give off or gain some electrons if this happens the atom becomes electrically charged the process in which an atom loses or gains electrons is called ionization when an atom does not have the same number of protons and electrons an ion is formed when an atom loses or gains one or more electrons it acquires a net electrical charge and it is called an ion for example a neutral magnesium atom has 12 protons and 12 electrons if the magnesium atom loses two electrons it will have a net electrical charge of positive 2. to find the net charge of an ion subtract the number of protons to the number of electrons in this case the net charge is equal to 12 which is the number of protons minus 10 which is the number of electrons since it lost two electrons therefore a magnesium ion has a net electrical charge of positive two a magnesium ion is represented with a symbol of magnesium with a charge of positive two [Music] a positive ion is called a cation when an atom loses an electron to another atom there is an imbalance in the number of protons and electrons in an atom when this happens the number of protons become greater than the number of electrons hence the atom becomes positively charged a negative ion is called an ion when an atom gains an electron given up by another atom an increase of negative particles happens for that atom when this happens the number of protons is less than the number of electrons in the particle the atom that has accepted electron during chemical combination becomes negatively an atom that gains extra electrons will have the same mass number and atomic number as the ion that was formed all atoms of the same element have the same atomic number that means they have the same number of protons however atoms do not necessarily have the same number of neutrons atoms with the same number of electrons and protons but different number of neutrons are called isotopes isotopes are atoms of the same element with different mass numbers the presence of isotopes disproved one of dalton's postulates in his atomic theory which states that all the atoms of the same element have the same properties two atoms are not alike if they have different mass numbers if the isotopes of an element have the same number of electrons then they will have the same chemical properties the chemical characteristics of a given atom depend only on the number of electrons in the atom and not the number of neutrons however isotopes of an element have slightly different physical properties the slight variation in their physical properties is due to the small difference in their relative masses [Music] most elements have at least two or three isotopes for example hydrogen has three known isotopes protium euterium and tritium which are symbolized as hydrogen one hydrogen 2 and hydrogen 3 the atomic masses of which are one atomic mass unit two atomic mass units and three atomic mass units respectively protium has one proton with no neutron euterium has one proton and one neutron tritium has one proton and two neutrons in these three isotopes take note that they all have one proton this is the atomic number identified for the hydrogen atom now let's wrap things up an atom consists of three subatomic particles called protons electrons and neutrons electrons are negatively charged particles found outside the nucleus protons are positively charged particles found inside the nucleus while neutrons are electrically neutral and are located in the nucleus of the atom an atom is identified by two numbers the atomic number and the mass number the atomic number is the number of protons in the nucleus of the atom the mass number represents the sum of the protons and neutrons in the nucleus of the atom the process in which an atom loses or gains electrons is called ionization when an atom loses or gains one or more electrons it acquires a net electrical charge and it is called an ion a positive ion is called a cation a negative ion is called an an ion isotopes are atoms of the same elements with different mass numbers that's all for now we will be discussing about how to use the periodic table to predict the chemical behavior of an element in our next video so stay tuned see you on our next video and don't 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Channel: The Learning Bees

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Keywords: The Learning Bees, Department of Education, DepEd, MELC-Based, Most Essential Learning Competencies, Science, MELC, Grade 8, Chemistry, difference of atom and molecule, atom, molecule, electron, neutron, proton, nucleus, electron cloud, Leucippus, Democritus, The Solid Sphere Model, Dalton, Atomic Theory of Matter, Plum-Pudding Model, Thomson, Nuclear Model, Rutherford, James Chadwick, Planetary Model, Bohr, Quantum Mechanical Model, Schrodinger, attomic number, mass number, cation, anion, isotopes

Id: VBjSs66M3Yo

Length: 15min 4sec (904 seconds)

Published: Fri May 21 2021