Science 8 Quarter 3 Lesson 3 Atoms: Inside Out PDF

Prepared by : CLASS DISCUSSION GERVY R. VALEROSO - Teacher II, Science Feb. 26 – March 1, 2024  In this lesson, you are going to learn about the number of protons, neutrons, and electrons in a particular atom. An atom is a basic unit of matter that consist...

Prepared by : CLASS DISCUSSION GERVY R. VALEROSO - Teacher II, Science Feb. 26 – March 1, 2024  In this lesson, you are going to learn about the number of protons, neutrons, and electrons in a particular atom. An atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.  WHAT’S NEW  Matter is made up of atoms that are too small to see with the unaided eye or even with the use of the ordinary light microscope.  When the ancient Greek Philosophers conceived the idea of an atom, they thought the atom is indivisible, that it has no parts.  Scientists have proven, however, that the atom is composed of even smaller particles.  WHAT’S NEW From experiments conducted in the latter part of the 19th century to the early half of the 20th century, scientists collected evidence that atoms are composed of three types of particles: proton, electron and neutron. These three subatomic particles of an atom contain different charges.  WHAT IS IT All matter is composed of an atoms. It is the basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons.  WHAT IS IT  In the earlier grades, you learned about magnets.  A magnet has two ends, two poles, the north and the south.  When you put the north ends of two magnets next to each other and the magnets move apart.  Also, when you put the two south ends next to each other, it will also move apart. They repel each other.  WHAT IS IT  When you placed the south and north ends next to each other, they will attract.  Similarly, in the concept of electric charges, the same charges will repel, and different charges will attract.  For example, when the plastic strips rubbed with the cloth causes the strips to become negatively charge. This happens because particles move from the cloth onto the plastic strips.  WHAT IS IT  Consider the charge on the cloth after the rubbing action, it will be positively charge.  This is what happened: the negative charge move from the cloth leaving the cloth positively charged.  When the plastic strips is hung over the wooden rod, the two halve of the strip move equally away from each other.  WHAT IS IT  The conclusion will be the forces are equal and acted on opposite directions.  Even the objects which seemed to be neutral can carry “charges”.  Particles which make up the atom are called subatomic particles.  The atoms composed of three subatomic particles such as protons, electrons and neutrons.  WHAT IS IT The proton carries a positive charge (+1). The electron carries a negative charge (-1). Atoms, in their most stable state are neutral with an equal number of protons and electrons  WHAT IS IT  Properties of the three subatomic particles based on their masses are summarized on table 1.  WHAT IS IT  Based on the table above, the masses of three subatomic particles have compared. The protons and neutrons are “massive indeed”.  WHAT IS IT  Electrons are very much lighter than the protons and neutrons, to the point that its mass does not significantly contribute to the mass of the entire atom. In effect, the mass of the electron is negligible.  WHAT IS IT  The massive part of the atom, then, comes from the masses of the protons and neutrons. Collectively, the protons and neutrons are called nucleons.  The nucleons, tightly packed together, form the nucleus in the center of an atom.  Thus, most of the mass of an atom is contained in its nucleus. You have also observed that electrons contain a negative charge and move around the nucleus of an atom.  WHAT IS IT  Democritus (400 BC)  Democritus was a Greek philosopher who was the first person to use the term atom (atomos: meaning indivisible).  He thought that if you take a piece of matter and divide it and continue to divide it you will eventually come to a point where you could not divide it any more.  This fundamental or basic unit was what Democritus called an atom.  WHAT IS IT  He called this the theory of the universe:  1. All matter consists of atoms, which are bits of matter too small to be seen.  2. There is an empty space between atoms.  3. Atoms are completely solid.  4. Atoms have no internal structure.  5. Each atom (of a different substance) is different in size, weight and shape.  WHAT IS IT  John Dalton (1800’s)  Solid Sphere / “Billiard Ball” Model  John Dalton was the first to adapt Democritus’ theory into the first modern atomic model.  His atomic model are:  1. All matter consists of tiny particles called atoms.  2. Atoms are indestructible and unchangeable.  3. Elements are characterized by the weight of their atoms.  4. When elements react, it is their atoms that have combined to form new compounds.  WHAT IS IT  Joseph John Thomson (1890’s)  Plum pudding Model / Raisin bread Model  When the idea of an atom was first proposed by the ancient Greeks, they thought it was a particle with no parts.  However the 19th century, J.J Thomson was able to discover that atoms have negatively-charged particles, which he called electrons.  It led him to propose a new model for an atom, which he called the plum pudding model. He also proposed that the negatively-charged electrons were embedded in a kind of cloud or soup of positive charge.  WHAT IS IT  These are the key points to Thomson’s Atomic Model:  1. Because of its design this model is known as the plum pudding model.  2. Each atom is a sphere filled with positively charged ‘fluid’. This resembles the sticky jam part of a pudding.  3. Corpuscles (later called electrons), are the negatively charged particles suspended in this ‘fluid’. This resembles the plums in the pudding.  4. He did not predict the movement of these electrons.  WHAT IS IT  Ernest Rutherford (1910’s)  Nuclear Atomic Model  A group of scientists composed of Ernest Rutherford, Johannes Wilhelm Geiger and Ernest Marsden tested Thomson’s model by bombarding a very thin sheet of gold foil with positively-charged alpha particles.  In their experiment, the nucleus was postulated as small and dense to account for the scattering of alpha particles from thin gold foil.  WHAT IS IT  The observations made by Rutherford led him to conclude that:  1. Very few of the (α) particles that practically bounced back towards the source and some that were deflected at smaller angles. Hence the positive charge in an atom is not uniformly distributed.  2. Major fraction of the (α) particles bombarded towards the gold sheet passed through it without any deflection, and hence most of the space in an atom is empty.  WHAT IS IT  The nuclear model of the atom proposed by Rutherford in 1912 is still the picture of the atom that we hold today.  The model described an atom as tiny, dense, positively charged core called a nucleus, in which nearly all the mass concentrated, around which the light, negative constituents, called electrons, circulates at some distance, much like planets revolving around the sun.  WHAT IS IT  Niels Bohr (1910’s)  Planetary Model  Niels Bohr agreed with the planetary model of the atom, but also knew that it had a few flaws.  Using his knowledge of energy and quantum physics he was able to perfect Rutherford’s model.  He was able to answer why the electrons did not collapse into the nucleus.  WHAT IS IT  He theorized that:  1. Electrons orbit the nucleus in orbits that have a specific size and energy.  2. The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.  3. Electrons reside in orbits. They move between each shell when gaining and losing energy.  4. When gaining energy, electrons move to closer orbit from the nucleus.  WHAT IS IT  Erwin Schrodinger (1920’s)  Quantum Mechanical Atomic Model / Electron Cloud Model  Schrodinger was a revolutionary physicist who used Heisenberg’s uncertainty principle to come up with the atomic model that we still use today.  WHAT IS IT  He discovered that:  1. Electrons don’t move around the nucleus in orbits.  2. Electrons exist in specific energy levels as a cloud.  3. The electron cloud is the region of negative charges, which surrounds the nucleus.  4. Orbital: The region with a high probability of containing electrons  WHAT IS IT  So far, you have learned about the three subatomic particles-protons, electrons, and neutrons, and how they arranged in the currently accepted model of an atom.  Among these subatomic particles have the number of protons of all elements is also known as the atomic number. Then, the mass number tells us the total number of protons + neutrons in the nucleus. Atomic mass gives us the relative mass of the individual.  WHAT IS IT  To understand more about the atomic mass, try to analyze the following information and examples given below.  Atomic symbols represent the atoms of all the elements.  Atomic symbol is a one-or-two letter notation used to represent an atom corresponding to a particular element.  When the symbol has two letters, only the first is capitalized.  WHAT IS IT  Atomic number, which is represented by a capital letter Z, is equal to the number of protons and electrons in the nucleus of an atom.  Mass number, also known as the Atomic Mass, has this formula:  To get for the number of neutron, derive the formula from the above formula of mass number:  WHAT IS IT  Example 1:  Compute for the number of proton, electron, and neutron of the element Magnesium (24Mg12).  Answer:  Atomic number = 12  Mass number = 24  Number of p+ = 12  Number of e- = 12  Number of n0 = 12  WHAT IS IT  Example 2:  Compute for the number of proton, electron, and neutron of the element Chlorine (35Cl17).  Answer:  Atomic number = 17  Mass number = 35  Number of p+ = 17  Number of e- = 17  Number of n0 = 18  WHAT IS IT  Example 3:  Compute for the number of proton, electron, and neutron of the element Tin (118Sn5o).  Answer:  Atomic number = 50  Mass number = 118  Number of p+ = 50  Number of e- = 50  Number of n0 = 68 WHAT’S MORE  Activity 4: Determining the Number of Protons, Electrons and Neutrons  Directions: Determine the atomic number, mass number and the correct numbers of protons, electrons, and neutrons of the following elements. Atomic # = 36 Mass # = 84 Protons = 36 Electron=36 Neutron=48 Atomic # = 6 Mass # = 12 Protons = 6 Electron= 6 Neutron= 6 WHAT’S MORE  Activity 5: Atomic Model - Direction: Complete the table below based on the given atomic model and proponent. Determining the number of protons, electrons and neutrons. Atomic Number Atomic Mass Atomic Atomic Number Mass Atomic Number Atomic Mass Atomic Number Atomic Mass Atomic Number Atomic Mass 1. Neutral Atoms When an atom has an equal number of electrons and protons, it has an equal number of negative (the electrons) and positive electric charges (the protons). As a result, the atom's total electric charge is zero, and it is said to be neutral. Therefore, all the elements in the periodic table are neutral atoms. An APE will help you to know the number of protons and electrons! nA =P=E Atomic number = Protons = Electrons nA =P=E Atomic number = Protons = Electrons Atomic Number of Number of Number Protons Electrons 8 8 8 nA =P=E Atomic number = Protons = Electrons Atomic Number of Number of Number Protons Electrons 12 12 12 nA =P=E Atomic Atomicnumber number= =Protons Proton == Electrons Electron Atomic Number of Number of Number Protons Electrons 20 20 20 nA =P=E Atomic Atomicnumber number= =Protons Proton == Electrons Electron Atomic Number of Number of Number Protons Electrons 30 30 30 Atomic Number ✓ Number of Protons ✓ Number of Electron ✓ Number of Neutrons? Number of neutron = atomic mass - atomic number Number of neutron = atomic mass - atomic number 16 8 8 Atomic Atomic Number of Mass Number Neutrons 16 8 8 Number of neutron = atomic mass - atomic number 24 12 12 Atomic Atomic Number of Mass Number Neutrons 24 12 12 Number of neutron = atomic mass - atomic number 65 30 35 Atomic Atomic Number of Mass Number Neutrons 65 30 35 Number of neutron = atomic mass - atomic number 39 19 20 Atomic Atomic Number of Mass Number Neutrons 39 19 20 Number of neutron = atomic mass - atomic number 84 36 48 Atomic Atomic Number of Mass Number Neutrons 84 36 48 ISOTOPES ISOTOPES Atoms with the same number of protons but different numbers of neutrons are called isotopes. They share almost the same chemical properties, but differ in mass and therefore in physical properties.  atomic mass atomic mass Both are carbon element but they have different number of neutrons and thus affecting their atomic mass since neutrons are the heaviest subatomic particle of atom.  atomic mass atomic mass Number of neutron = atomic mass - atomic number Isotope Atomic Atomic Number of Mass Number Neutrons C-12 12 6 6 C-13 13 6 7 * Different number of neutrons Number of neutron = atomic mass - atomic number Isotope Atomic Atomic Number of Mass Number Neutrons Ne-20 20 10 10 Ne-21 21 10 11 * Different number of neutrons Number of neutron = atomic mass - atomic number Isotope Atomic Atomic Number of Mass Number Neutrons Cl-35 35 17 18 Cl-37 37 17 20 * Different number of neutrons Atomic Mass = Neutrons + Protons Atomic Mass = Neutrons + Protons Element Number Number Atomic of Protons of Mass Neutrons Carbon 6 6 12 Carbon 6 7 13 Atomic Mass = Neutrons + Protons Element Number Number Atomic of Protons of Mass Neutrons Oxygen 8 9 17 Oxygen 8 10 18  O-16, O-17, O-18 Isotope Atomic Atomic Number of Mass Number Neutrons O-16 16 8 8 O-17 17 8 9 O-18 18 8 10  Ca-40, Ca-45, Ca-48 Isotope Atomic Atomic Number of Mass Number Neutrons Ca-40 40 20 20 Ca-45 45 20 25 Ca-48 48 20 28 ION An ion is a charged atom or molecule. It is charged because the number of electrons do not equal the number of protons in the atom or molecule. An atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom. Element Atomic Atomic Number Number Number Charge Mass Number of Proton of of Electron Neutron Oxygen 16 8 8 10 8 -2 Element Atomic Atomic Number Number Number Charge Mass Number of Proton of of Electron Neutron Magnesium 24 12 12 10 12 +2 27 59 Element Atomic Atomic Number Number Number Charge Mass Number of Proton of of Electron Neutron Cobalt 59 27 27 25 32 +2 Element Atomic Atomic Number Number Number Charge Mass Number of Proton of of Electron Neutron Sulfur 32 16 16 18 16 -2