CHEMISTRY Atomic Structure OBJECTIVES •State the relative charges and approximate relative masses of proton, neutrons and electrons •Define proton number (atomic number) as the number of protons in the nucleus of an atom OBJECTIVES •Define nucleon number (mass number) as the total number of protons and neutrons in the nucleus of an atom •Use proton number and the simple structure of atoms to explain the basis of the Periodic Table, with special reference to the elements of proton number 1-20 WHAT IS AN ATOM? • Atom is the very small part of an element, which provides specific properties of that element • For example, gold is an element, it is composed of many gold atoms joining together WHAT IF WE EXAMINE EACH INDIVIDUAL ATOM… • It is found that atom is composed of subatomic particles. SUBATOMIC PARTICLES • Each individual atom is composed of subatomic particles, including proton, neutron and electron PROTON, NEUTRON AND ELECTRON Proton Neutron Electron Charge Positive charge (+ve) Neutral Negative charge (-ve) Relative mass 1 1 1/1837 Location Nuclei Nuclei Around the atom PROTON •Located at the centre of the atom (nuclei) •Positively charged Atomic diagram of helium PROTON • Number of proton equals to atomic number • From1,2,3......up to 118 • contributes to the mass number of the element atom Atomic diagram of helium •How can we know the atomic number of an element? LOOK AT THE PERIODIC TABLE • Top corner of the symbol • When an atom has two protons in the nuclei, the atomic number is 2. • That is Helium. QUIZ CHECK •What element is it when atomic number is: i. ii. iii. iv. v. 6 8 12 17 19 PROTON, NEUTRON AND ELECTRON - ✅ Neutron Electron Charge Positive charge (+ve) Neutral Negative charge (-ve) Relative mass 1 1 1/1837 Location Nuclei Nuclei Around the atom Proton NEUTRON •Located at the centre of the atom (nuclei) •Neutral in charge Atomic diagram of helium NEUTRON It is found that: neutron in the nuclei contributes to the mass number of the element atom Atomic diagram of helium MASS NUMBER/ NUCLEON NUMBER Number of proton + number of neutron Atomic diagram of helium MASS NUMBER/ NUCLEON NUMBER MASS NUMBER/ NUCLEON NUMBER PROTON, NEUTRON AND ELECTRON - ✅ Neutron Charge Positive charge (+ve) Neutral Negative charge (-ve) Relative mass 1 1 1/1837 Location Nuclei Nuclei Around the atom Proton ✅ Electron •Moving around the nuclei, form an electron cloud •Negatively charged •Always equals to the number of proton if the atom itself is neutrally existing ELECTRON ELECTRON •It does not affect the mass of element atom •Determines the chemical properties of elements PROTON, NEUTRON AND ELECTRON - ✅ Neutron Charge Positive charge (+ve) Neutral Negative charge (-ve) Relative mass 1 1 1/1837 Location Nuclei Nuclei Around the atom Proton ✅ Electron ✅ SHORT SUMMARY • 3 subatomic particles of an atom: proton, neutron, electron • Proton (+ve) - Centre of atom (nuclei) - Atomic number • Neutron - Centre of atom (nuclei) - Neutron + proton = mass number • Electron (-ve) - Moves around the nuclei - QUICK CHECK QUICK CHECK QUICK CHECK QUICK CHECK QUICK CHECK CHECK PERIODIC TABLE •Can you find out how do the elements are arranged in the periodic table? •Random/ systematic arrangement? CHECK PERIODIC TABLE •How are the elements arranged in periodic table? •The arrangement of element in periodic table is based on the number of proton. ISOTOPE ISOTOPE - HYDROGEN • Number of proton = 1 ISOTOPE - HYDROGEN • Number of proton = 1 Hydrogen • Hydrogen and deuterium are the same element, they have same number of proton but different number of neutron Neutron ISOTOPE - HYDROGEN • Number of proton = 1 Hydrogen • They have the same proton number but a different nucleon number Neutron ISOTOPE - HYDROGEN • Number of proton = 1 Hydrogen • They have the same proton number but a different nucleon number • They are ISOTOPE. Neutron ISOTOPE - CHLORINE • Number of proton = 17 Chlorine ISOTOPE - CHLORINE • Number of proton = 17 Chlorine • Chlorine-35 and Chlorine-37 are the same element, they have same number of proton but different number of neutron ISOTOPE - CHLORINE • Number of proton = 17 Chlorine • Chlorine-35 and Chlorine-37 are the same element, they have same number of proton but different number of neutron • They are ISOTOPE. LOOK AT CHLORINE IN THE PERIODIC TABLE • What does 35.5 mean? LOOK AT CHLORINE IN THE PERIODIC TABLE • What does 35.5 mean? • It is called relative atomic mass. LOOK AT CHLORINE IN THE PERIODIC TABLE • What does 35.5 mean? • It is called relative atomic mass. • Determined by: - relative isotopic mass - relative abundance EXAMPLE - CHLORINE • It is found that there are two naturally occurring isotopes, 35Cl and 37 Cl, with relative abundances of 75.4% and 24.6% respectively. Calculate the relative atomic mass of chlorine EXAMPLE - CHLORINE • It is found that there are two naturally occurring isotopes, 35Cl and 37 Cl, with relative abundances of 75.4% and 24.6% respectively. Calculate the relative atomic mass of chlorine 35 Cl Number of proton: Number of neutron: Number of electron: 37 Cl Number of proton: Number of neutron: Number of electron: EXAMPLE - CHLORINE • It is found that there are two naturally occurring isotopes, 35Cl and 37 Cl, with relative abundances of 75.4% and 24.6% respectively. Calculate the relative atomic mass of chlorine Chlorine 35 Cl 37 Cl Abundance (%) 75.4 24.6 EXAMPLE - CHLORINE • It is found that there are two naturally occurring isotopes, 35Cl and 37 Cl, with relative abundances of 75.4% and 24.6% respectively. Calculate the relative atomic mass of chlorine Chlorine 35 Cl 37 Cl Abundance (%) 75.4 24.6 35 x 75.4% + 37 x 24.6% =35.5 PRACTICE • It is found that there are three naturally occurring isotopes, 16O, 17O and 18O, with relative abundances of 99.76%, 0.04% and 0.20% respectively. Calculate the relative atomic mass of oxygen. PRACTICE • It is found that there are three naturally occurring isotopes, 16O, 17O and 18O, with relative abundances of 99.76%, 0.04% and 0.20% respectively. Calculate the relative atomic mass of oxygen. Lithium 16 O 17 O 18 O Abundance (%) 99.76 0.04 0.20 PRACTICE • It is found that there are three naturally occurring isotopes, 16O, 17O and 18O, with relative abundances of 99.76%, 0.04% and 0.20% respectively. Calculate the relative atomic mass of oxygen. Lithium 16 O 17 O 18 O Abundance (%) 99.76 0.04 0.20 16 x 99,76% + 17 x 0.04% + 18 x 0.20% =16.0044 RADIOACTIVE & NON-RADIOACTIVE ISOTOPE •What is radioactive? RADIOACTIVE & NON-RADIOACTIVE ISOTOPE •What is radioactive? •It is the emission of ionized radiation or particles RADIOACTIVE & NON-RADIOACTIVE ISOTOPE •Radioactive isotope: has a very unstable nucleus energy of radiation decays or emits excess •E.g. carbon-14, detect the ulcer-causing bacteria Heliobacter pylori RADIOACTIVE & NON-RADIOACTIVE ISOTOPE • Do carbon 12 and carbon 14 have same chemical properties? Do carbon 12 and carbon 14 have same number of : i. proton, ii. neutron and iii. electron? What does it tell you? ELECTRON •It does not affect the mass of element atom •Determines the chemical properties of elements RADIOACTIVE & NON-RADIOACTIVE ISOTOPE • Do carbon 12 and carbon 14 have same chemical properties? Do carbon 12 and carbon 14 have same number of : i. proton, ii. neutron and iii. electron? What does it tell you? Same number of outermost electron similar chemical properties SUMMARY • What is isotope? Element atoms with They have the same proton number but a different nucleon number • How many types of isotopes? Radioactive, non-radioactive • Do both isotopes have same chemical properties? APPLICATION •Form a group of 3 or 4 •Find out medical/ industrial use of radioactive isotopes •Make a PPT file for presentation (within 5 mins) •8/3/2019 (Fri) RADIOACTIVE ISOTOPE Isotope Group Calcium 47 Cobalt 60 Copper 64 Iridium 192 Californium 252 Uranium 235 3 2 1 4 5 6 • Describe the application • Please indicate the half life of that radioactive isotope, how does it correspond the application? • How should we dispose it? WHO AND HOW TO DISCOVER SUBATOMIC PARTICLES? Group • • • • Cathode-ray tube (CRT) Millikan’s oil-drop experiment Rutherford’s alpha-particle experiment Chadwick experiment 6 5 4 3 Background (hypothesis? Anything trigger scientists’ thinking?) Describe and explain the experiment/ model State the significance to the development of atomic structure Video recording with English subtitle (no more than 5 mins) Thomson’s Particle plum-pudding radiation from model v.s. radioactive modern materials atomic model 2 1