Topic: Isotopes of elements part 1

Target group

Elementary school student (grades 7. and 8.)

Core curriculum

Elementary school. Chemistry.

I. Internal structure of matter. Pupil:

4) defines the concept of isotope; describes the differences in the structure of isotope atoms, e.g. hydrogen; searches for information on the uses of different isotopes.

General aim of education

The student defines the concept of the element isotope.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• explain what are isotopes;

• describe isotopes with symbols;

• discuss differences in the structure of hydrogen isotope atoms;

• calculate the mass of the isotope.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• exposing

  • film.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

Realization

1. The teacher - in order to remind students about the structure of the atom - asks questions, e.g.: „What is the atom?”, „What types of elementary particles are part of the atom?”, „What elementary particles are in the nucleus and which are outside the nucleus?”. Then he asks for a reminder of the concepts: atomic number, atomic mass, atomic mass unit.

2. Students read the fragment titled „Differences in the atoms of the same element” and in their own words they explain the concept of isotope. Then, the teacher asks the proteges to consider whether the isotopes of the same element have the same atomic and mass numbers, and if not, which of these numbers may be different and why. The answers accepted by the teacher, students write in the form in the abstract.

3. The teacher presents the table showing nitrogen isotopes. He asks students for her joint analysis: he draws attention to the description of the isotopes of the element by the symbol.

4. Students carry out the task number 2: using periodic table that shows the percentage of stable isotopes of particular elements, they determine how many elements have only one natural type of isotope and which elements have the most of them.

5. Students read the fragment titled „Isotopes of hydrogen in nature”. They analyze illustration and the table showing the properties of hydrogen isotopes. Then, working in pairs, they ask each other about the knowledge of the fragment.

6. The teacher plays the presentation titled „Potassium isotopes”. After the screening, students answer the following questions: „Which of the types of the element are stable?”, „What is the application of its isotopes?”. They write their answers in the form. The indicated persons read them.

7. Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

Summary

1. Teacher asks: If there was going to be a test on the material we have covered today, what questions do you think would you have to answer? If the students do not manage to name all the most important questions, the teacher may complement their suggestions.

2. The teacher asks the students to finish the following sentences:

   • Today I learned ...

   • I understood that …

   • It surprised me …

   • I found out ...

   The teacher can use the interactive whiteboard in the abstract or instruct students to work with it

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Isotopes of elements part 1

Atoms belonging to the same element have the same nucleus charge (identical number of protons) and the same number of electrons moving around the nucleus. However, as it turns out, these atoms can differ in mass. The reason for this phenomenon is the possibility that different numbers of neutrons occurs in the nucleus of atoms of the same element. Those atoms that have more neutral particles have a larger mass.

The atoms of the element with the same number of protons, and different number of neutrons in the nucleus are called isotopes.

The element with several isotopes is nitrogen. There are seven neutrons in the nucleus of one of them, and in the nucleus of the other – eight neutrons. Each of these isotopes has the same number of protons that can be found in the periodic table.

The information on the number of neutrons isotopes contain is important in their description. Therefore, mainly mass number providing information on the number of these particles is used in its description. The atomic number is usually omitted due to the fact that it can be found in the periodic table.

Isotopes are presented in two ways: the mass number is placed in the upper index on the left side of the symbol of the element or after the dash after the name of the element, e.g. ${}^{\text{14}}\text{N}$ or nitrogen‑14.

Isotopes with the same atomic number belong to the same element. In principle, these show identical properties, with the only exception being hydrogen isotopes. The hydrogen in nature is a mixture of mainly two isotopes in stable‑state: ${}^{\text{1}}\text{H}$ (99.985%) and ${}^{\text{2}}\text{H}$ (0.015%). It means that of 100,000 atoms of hydrogen, 99,985 are isotopes ${}^{\text{1}}\text{H}$, and 15 atoms – isotopes ${}^{\text{2}}\text{H}$. There is also the third, unstable isotope ${}^{\text{3}}\text{H}$. It occurs in trace amounts. The isotopes of hydrogen were the only ones in the world of elements to have their names: protium, deuterium and tritium.

Symbol of hydrogen isotope
${}^{\text{1}}\text{H}$ or hydrogen‑1
Name of hydrogen isotope – protium

Symbol of hydrogen isotope
${}^{\text{2}}\text{H}$ or hydrogen‑2
Name of hydrogen isotope – deuterium

Symbol of hydrogen isotope
${}^{\text{3}}\text{H}$ or hydrogen‑3
Name of hydrogen isotope – tritium

It is easy to see that hydrogen isotopes differ in the number of nucleons. For this reason, there is a large mass difference between them, for example the deuterium atom has a mass twice as large as the weight of the protium and the tritium mass is three times larger than protium. This phenomenon affects the properties of these isotopes: protium, deuterium and tritium have different properties.

• Isotopes are atoms of the same chemical element that have the same number of protons and different number of neutrons.

• Most of the chemical elements found in nature are a mixture of isotopes with a stable composition.

• Isotopes of hydrogen are: protium (${}^{\text{1}}\text{H}$), deuterium (${}^{\text{2}}\text{H}$) and tritium (${}^{\text{3}}\text{H}$). Their properties are different.