3. Lesson 2 QUARTER 2_Isotopes and Atomic Mass.pptx

ISOTOPES

1. 1. The learners draw the structure of an atom in terms of the nucleus and electron shells within an atom; and differentiate the subatomic particles — protons, neutrons, and electrons —in terms of their symbol, mass, charge, and location within an atom .

2. 1. Define isotopes and explain their significance in atomic structure. 2. Calculate atomic mass using the relative abundance of isotopes. 3. Compare isotopes of an element in terms of number of neutrons and mass number. 4. Explain the concept of atomic mass and how it is calculated. 5. Draw and label isotopes of a given element. 6. Discuss how isotopes influence the average atomic mass of an element.

3. + - Electron Proton Neutron Nucleus Electron shell

4. Answer: Oxygen What element is this? How many valence electrons are there in oxygen? Answer: 6 valence electrons

5. 1. What happens if the number of protons in an atom changes ? Answer: The atom becomes a different element . 2. Why is the number of protons called the atomic number ? Answer: Because it uniquely identifies the element .

6. ELement Number of protons Number of electrons Number of Neutrons Carbon-12 6 6 6 Carbon-13 6 6 7 Carbon-14 6 6 8 What can you observe in the table ? Answer: They have different numbers of neutrons .

7. ELement Number of protons Number of electrons Number of Neutrons Carbon-12 6 6 6 Carbon-13 6 6 7 Carbon-14 6 6 8 What do you call atoms of the same element that have different numbers of neutrons ? Answer: Isotopes

8. Activity No.: Activity #1: Shape Up Your Science Words! Objective(s): Students will identify and correctly spell key vocabulary words related to atoms and isotopes by arranging shapes in the correct order based on given clues. Materials Needed: Powerpoint presentation Instructions: Read the definition provided at the top of the page. Look at the arrangement of shapes at the top (with letters) and match it to the shapes at the bottom. Rearrange the shapes at the bottom to match the top arrangement and reveal the correct vocabulary word.

9. S O T O P E S I IS OT OP ES CLUE: Atoms of the same element with different numbers of neutrons.

10. AT OM IC NU MB ER CLUE: Defined by the number of protons, which remain constant across isotopes. (Two words) A O M I C N U T M B E R

11. MA SS NU MB ER CLUE: The sum of protons and neutrons, which varies among isotopes. (Two words) M S U N A M B R E S

12. AT OM IC MASS CLUE: The weighted average mass of an element's isotopes, based on their relative abundance. (Two words) A O M I C M A T S S

13. CLUE: The proportion of each isotope present in a sample. (Two words) E L T A I V E R B U D N A N C A E RE LA TI VE AB UN DA NC E

14. Activity No.: Activity #2: Exploring the Importance of Isotopes Objective(s): To understand the significance of isotopes in science by examining selected examples and discussing their applications in various fields. Materials Needed: Powerpoint presentation Instructions: Review the selected isotopes provided and familiarize yourself with their basic properties. Participate in a class discussion about the importance and applications of these isotopes in real-life situations. Answer the guide questions based on the discussion and your understanding of the topic.

15. Technetium-99 Isotopes such as Technetium-99 are crucial in diagnostic imaging, allowing for non-invasive internal scans to detect medical conditions .

16. Carbon-14 Carbon-14 helps scientists determine the age of fossils , artifacts, and geological samples , providing valuable information about past civilizations and natural history.

17. Cobalt-60 Cobalt-60 is applied in radiation therapy to target and destroy cancer cells while minimizing damage to surrounding healthy tissue.

18. Uranium-235 Isotopes like Uranium-235 are used as fuel in nuclear reactors to generate power through nuclear fission.

19. Why do scientists use isotopes instead of regular atoms in some experiments? Answer: Scientists use isotopes instead of regular atoms because isotopes can have special properties , like being radioactive, which help in experiments, medical imaging, or dating samples . For example, Carbon-14 is used to find the age of fossils .

20. Activity No.: Activity #3: Mastering Atomic Number, Mass Number, Atomic Mass, and Relative Abundance Objective(s): To understand and apply the concepts of atomic number, mass number, atomic mass, and relative abundance through guided discussion and calculation exercises. Materials Needed: Powerpoint presentation Instructions: Listen and participate actively in the discussion about atomic number, mass number, atomic mass, and relative abundance. Take note of the formulas and examples provided for calculating atomic mass and interpreting relative abundance. Solve the given calculation problems accurately and answer the guide questions based on your understanding of the lesson.

21. ATOMIC NUMBER The number of protons in an atom. MASS NUMBER The total number of protons and neutrons in an atom. ATOMIC MASS The atomic mass is the weighted average mass of an element's isotopes based on their natural abundance. It reflects the average mass of all the isotopes of an element (Hill & Kolb, 2001). RELATIVE ABUNDANCE The relative abundance of an isotope is the percentage of that isotope found in nature. It is used to calculate the atomic mass of an element.

22. CARBON Number of Protons 6 Atomic Number OXYGEN Number of Protons 8 Atomic Number NITROGEN Number of Protons 7 Atomic Number HYDROGEN Number of Protons 1 Atomic Number 6 8 7 1 AT OM IC NU MB ER

23. CARBON Number of Protons 6 Number of Neutrons 6 MASS NUMBER NITROGEN Number of Protons 7 Number of Neutrons 7 MASS NUMBER OXYGEN Number of Protons 8 Number of Neutrons 8 MASS NUMBER HYDROGEN Number of Protons 1 Number of Neutrons MASS NUMBER 12 16 14 1 MA SS NU MB ER

24. RE LA TI VE AB UN DA NC E CARBON Carbon-12 → 98.9% abundance Carbon-13 → 1.1% abundance CHLORINE Chlorine-35→ Relative abundance = 75% Chlorine-37→ Relative abundance = 25% NITROGEN Nitrogen-14→ Relative abundance = 99.63% Nitrogen-15→ Relative abundance = 0.37% BROMINE Bromine-79→ Relative abundance = 50.7% Bromine-8→ Relative abundance = 49.3%

25. AT OM IC MA SS Atomic Mass=∑(isotope  mass×relative  abundance) Step 1: Convert abundance percentages to decimals. Step 2: Multiply each mass by its decimal abundance. Step 3: Add the results. Step 4: Round to appropriate significant figures (based on given data → 4 sig figs).

26. AT OM IC MA SS Problem 1: Chlorine has two main isotopes: Chlorine-35 : Mass = 34.969 amu, Abundance = 75.8% Chlorine-37 : Mass = 36.966 amu, Abundance = 24.2% Question: Calculate the atomic mass of Chlorine. Step 1: Convert abundance percentages to decimals. Cl-35: Abundance = 75.8% → 0.758 Cl-37: Abundance = 24.2% → 0.242

27. AT OM IC MA SS Problem 1: Chlorine has two main isotopes: Chlorine-35 : Mass = 34.969 amu, Abundance = 75.8% Chlorine-37 : Mass = 36.966 amu, Abundance = 24.2% Question: Calculate the atomic mass of Chlorine. Cl-35: 34.969 X 0.758 = 26.507 Cl-37: 36.966 X 0.242 = 8.946 Step 2: Multiply each mass by its decimal abundance.

28. AT OM IC MA SS Problem 1: Chlorine has two main isotopes: Chlorine-35 : Mass = 34.969 amu, Abundance = 75.8% Chlorine-37 : Mass = 36.966 amu, Abundance = 24.2% Question: Calculate the atomic mass of Chlorine. 26.507 + 8.946 Step 3: Add the results. Step 4: Round to appropriate significant figures (based on given data → 4 sig figs). Atomic Mass ≈35.453  amu ​

29. Problem 2: Magnesium Given: Mg-24: Mass = 23.985 amu, Abundance = 78.99% Mg-25: Mass = 24.986 amu, Abundance = 10.00% Mg-26: Mass = 25.983 amu, Abundance = 11.01% Atomic Mass=∑(isotope  mass×relative  abundance) Mg-24: Abundance = 78.99% → 0.7899 Mg-25: Abundance = 10.00% → 0.1000 Mg-26: Abundance = 11.01% → 0.1101 Mg-24: 23.985 x 0.7899 = 18.946 Mg-25: 24.986 x 0.1000 = 2.499 Mg-26: 25.983 x 0.1101 = 2.860 18.946+2.499+2.861 Atomic Mass ≈24.31 amu​

30. 1. Weighted Average: The atomic mass of an element is calculated by taking the average of all its isotopes’ masses , considering how common each isotope is. 2. More Abundant Isotope: The isotope that occurs more often has a bigger effect on the average atomic mass, pulling it closer to its own mass.

31. 3. Less Abundant Isotope: Rare isotopes contribute less , so they only slightly change the atomic mass away from the most common isotope. 4. Not a Whole Number: Because the atomic mass is an average of different isotopes , it is usually a decimal, not an exact whole number like the mass of individual isotopes.

32. 4. Element Identity: Different isotopes of an element have the same chemical behavior , but the mix of isotopes changes the measured atomic mass.

33. 1. Why is the atomic mass of an element usually not a whole number ? 2. Which isotope affects the atomic mass more: the more abundant one or the less abundant one ? Answer: Because it is a weighted average of all the element’s isotopes , not just one isotope. Answer: The more abundant isotope .

34. Assessment of identifying and labeling isotopes 1. What do you call the atoms of the same element with different numbers of neutrons ? Isotopes

35. 2. Label the following isotopes of Carbon: C-12, C-13, C-14 Indicate the number of protons, neutrons, and electrons for each isotope. ISOTOPES Number of protons Number of Neutrons Number of Electrons C-12 C-13 C-14 Answer: 6 6 6 6 6 6 6 7 8

36. 3. How do isotopes of an element differ from each other ? 4. Which isotope of Hydrogen has one proton and one neutron ? 5. Why do isotopes of the same element have the same chemical properties ? Answer: Isotopes differ in the number of neutrons and hence their mass number. Answer: Deuterium (2 H 2 H). Answer: Isotopes have the same chemical properties because they have the same number of protons and electrons , which determine chemical behavior.

37. Day 2: Worksheet on atomic mass calculations 1. Calculate the atomic mass of Boron given the following isotopes: - Boron-10: Mass = 10.0129 amu, Abundance = 19.9% - Boron-11: Mass = 11.0093 amu, Abundance = 80.1%

38. Answer 1: Step 1 – Convert percentage abundance to fractional abundance: Boron-10: 19.9% → 0.199 Boron-11: 80.1% → 0.801 Step 2 – Multiply mass by fractional abundance: Boron-10: 10.0129×0.199=1.993 Boron-11: 11.0093×0.801=8.818 Step 3 – Add the results: 1.993+8.818 = 10.811 amu Step 4 – Round appropriately: Atomic Mass≈10.81 amu ​

39. 2. Determine the atomic mass of Neon using its isotopes: - Neon-20: Mass = 19.9924 amu, Abundance = 90.48% - Neon-21: Mass = 20.9938 amu, Abundance = 0.27% - Neon-22: Mass = 21.9914 amu, Abundance = 9.25% 3. What is the atomic mass of Chlorine given these isotopes? - Chlorine-35: Mass = 34.9689 amu, Abundance = 75.78% - Chlorine-37: Mass = 36.9659 amu, Abundance = 24.22%

40. Answer 2: Step 1 – Convert percentage abundance to fractional abundance: Neon-20: 90.48% → 0.9048 Neon-21: 0.27% → 0.0027 Neon-22: 9.25% → 0.0925 Step 2 – Multiply mass by fractional abundance: Neon-20: 19.9924×0.9048=18.08737952 Neon-21: 20.9938×0.0027=0.05668226 Neon-22: 21.9914×0.0925=2.0346995 Step 3 – Add the results: 18.08737952+0.05668226+2.0346995=20.17876128 Step 4 – Round appropriately: Atomic Mass≈20.18 amu ​

41. Answer 3: Step 1 – Convert percentage abundance to fractional abundance: Chlorine-35: 75.78% → 0.7578 Chlorine-37: 24.22% → 0.2422 Step 2 – Multiply mass by fractional abundance: Chlorine-35: 34.9689×0.7578=26.50482442 Chlorine-37: 36.9659×0.2422=8.95082998 Step 3 – Add the results: 26.50482442+8.95082998=35.4556544 Step 4 – Round appropriately: Atomic Mass≈35.46 amu ​

42. Day 3: Comparison chart of isotopes 1. What is the primary difference between isotopes of the same element ? Answer: The primary difference is the number of neutrons .

43. 2. Why is Carbon-14 used in radiocarbon dating but not Carbon-12? 3. How does the mass number of an isotope affect its atomic mass ? Answer: Carbon-14 is radioactive and decays over time , making it useful for dating, whereas Carbon-12 is stable. Answer: The mass number directly influences the atomic mass as it is the sum of protons and neutrons .

44. Day 4: Presentation on isotope’s applications 1. Explain one application of Carbon-14 in archaeology. Answer: Carbon-14 is used in radiocarbon dating to determine the age of archaeological samples by measuring the decay of C-14 .

45. 2. How is Technetium-99 used in medical diagnostics? 3. What role do isotopes play in nuclear power generation ? Answer: Technetium-99 is used in medical diagnostics as a radioactive tracer in imaging to detect abnormalities in organs . Answer: Isotopes like Uranium-235 are used as fuel in nuclear reactors to generate power through nuclear fission.