Module 2.3 Atomic Structure and Isotopes - PDF

Good Afternoon! Submission of Assignments Recall of Previous Discussion ITCOMA UEBMNR SAMS MUENBR MTAOIC SASM SPITOEO CEBAUNDAN CLAIOTNCULA Atomic Mass, Mass Number, and Isotopes Learning Objectives: : a.Determine the atomic number and mass number of different elements;...

Good Afternoon! Submission of Assignments Recall of Previous Discussion ITCOMA UEBMNR SAMS MUENBR MTAOIC SASM SPITOEO CEBAUNDAN CLAIOTNCULA Atomic Mass, Mass Number, and Isotopes Learning Objectives: : a.Determine the atomic number and mass number of different elements; b.Calculate the number of protons, electrons, and neutrons in each element; c.Identify the different isotopes of atoms; d.Determine the isotope abundance of an element.  DEFINITION OF TERMS Mass number – The mass number, also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units.  DEFINITION OF TERMS Atomic Mass – The atomic mass, also called atomic weight, is the weighted average mass of an element’s atoms, taking into account all its naturally occurring isotopes and their relative abundances. It is measured in atomic mass units (amu) or Daltons (Da).  DEFINITION OF TERMS Atomic Number – the number of protons in the nucleus of an atom. Note: no. of protons = no. of electrons (neutral atom) LEARNING CHECKPOINT! What is the atomic number, atomic mass, and mass number of beryllium?  DEFINITION OF TERMS Isotopes – are forms of an element that have different numbers of neutrons. All isotopes of an element have the same atomic number and number of protons, but they have different atomic masses from each other. Isotopes of an element share similar chemical properties, but have different nuclear properties. HOW TO WRITE AN ISOTOPE? C A Where: A – mass Z number Z – no. of protons C - element EXAMPLES 11 Ne Sn 20 9 10 50 SOME ELEMENTS AND THEIR ISOTOPE ABUNDANCE  LEARNING CHECKPOINT!  LEARNING CHECKPOINT!  LEARNING CHECKPOINT! How do we calculate the number of protons, electrons, and neutrons in an element? REMEMBER : : Atomic number = no. of protons No. of protons = no. of electrons (neutral atom) Mass number = protons + neutrons  Where: A=n+Z n = no. of neutrons A = mass number Z = no. of protons Example: 1. How many neutrons does an atom with a mass number of 79 and 35 electrons have? Solution: A=n+Z n=A–Z = 79 - 35 = 44 Example: 2. How many protons does the element with a mass number 35 have if it has 18 neutrons? Solution: A=n+Z Z=A-n = 35 - 18 = 17 Example: 3. How many electrons does an atom with a mass number 39 and atomic number 19 have? Solution: 19, because in a neutral atom, a proton is equal to electron LEARNING CHECKPOINT! How many neutrons are there in an ion with a mass number of 127 and 54 electrons that has a charge of -1Solution: have? n=A–Z = 127 – 53 = 74 Symbo Proton Neutr Electr Charg Mass l Si s ons ons e 2 No.28 14 7 14 12 10 + 3- 14 N 3- 7  SUMMARY The mass number (A) is the sum of the number of protons (atomic number, Z) and neutrons. Any element has always the same number of protons regardless of what isotope it is. The number of protons and electrons is equal in a neutral atom. QUESTIONS?