Atoms and elements

1. Atoms and elements Lesson 7

2. The standards • The standards for this lesson are • Recognize that all matter consists of atoms; identify the atomic mass and number, number of protons and electrons from the periodic table. • Identify atoms as the fundamental particles that make up matter. • Explain that all matter has properties that are determined by the structure and arrangement of its atoms.

3. pretest • Number to five. • #1 What is the chemical symbol for iron?

4. Pretest #2 • Sodium (Na-atomic number 11) is an element that is found in table salt. Explain how many electrons are in a neutral atom of sodium.

5. Pretest #3 • Which atomic particle is positively charged?

6. Pretest #4 • You are an electron involved in chemical reactions. Where are you found?

7. Pretest #5 • What is the atomic number of an atom that contains 26 protons, 29 neutrons, and 26 electrons? How do you know?

8. First-vocab • By the end of this lesson, you will be able to explain what these words mean. List them now. Skip a few lines. • Atom • Element • Nucleus • Proton • Neutron • Electron • Electron cloud • Energy level • Atomic number • Neutral • Atomic mass • Chemical symbol

9. What you will learn • Everything around us has mass and takes up space. • Everything around us-even living things-are made out of matter. • So, what makes up matter? • In this lesson, we will discuss the basic building blocks of all the things around us.

10. So, what’s the matter? • What do you think matter is? • Matter describes all of the physical substances around us. • Your pencil, your body, the table, the parts of experiments are all made of matter. • If it is matter, it can be seen, tasted, smelled, touched, and measured. • Matter does not, however, include heat, sound, or light.

12. Atoms and elements • What is an atom? • They are the basic building blocks of most of the matter around you. • Matter is made from atoms. • There are different kinds of atoms. • Each kind is an element. • An element is a pure substance that cannot be broken down into simpler substances by ordinary means.

13. The elements • We have looked at several elements. • Where are they? • About 118 elements have been discovered from all over the world. • Ninety of these are found in nature. • The rest are man made. • The synthetic elements will only last a short time before they break down. • Tell me five natural elements.

14. An atom is the smallest particle of an element that has all the properties of that element. • So, an atom of gold would be one particle of gold. • The atoms of every element are different. • To understand how the atoms of each element are different, we look at the particles that make up each atom.

16. The parts of an atom • Every atom has four main parts. • The nucleus-the core of the atom. The nucleus of most atoms if made up of two kinds of subatomic particles: protons and neutrons. • The protons-carry a positive charge + • The neutrons-carry no charge N • The electrons-carry a negative charge -

18. The Masses • The masses of protons and neutrons are measured in atomic mass units (amu). • Protons have a mass of about 1 amu. • Neutrons have a mass of about 1 amu. • The mass of electrons is insignificant compared with the mass of protons and neutrons.

19. More about electrons… • The electrons move around the atom in an area outside the nucleus. • This area is called the electron cloud. • The electron cloud is organized into energy levels. • There are several energy levels in an atom. • The outermost energy level is the level where chemical reactions take place. • During these chemical reactions, atoms gain, lose, or share the electrons in the outermost level.

20. The Electron Cloud of Uranium

21. Electron Clouds/shells • Electron rings can only hold a certain number of electrons. • The first ring holds 2 Electrons. • The second ring holds 8 Electrons. • The third ring holds 18 Electrons. • The fourth ring holds 36 Electrons. • That gets us through element 64-Gadolinium

22. Elements and subatomic particles • The properties of an element are determined by the structure of its atoms. So, gold is gold because of its atoms and their structure. • The number of protons in an atom is its atomic number. • The atomic number is the main feature used to distinguish the atoms of different elements. • We have used atomic numbers in our look at the elements. • No two elements have the same atomic number.

23. Atomic numbers • The atomic number is the number of protons in an atom. • In a neutral atom, the number of protons + equals the number of electrons -. • For example, oxygen has eight protons. • Therefore, its atomic number what? • And, how many electrons does it have? • The number of neutrons, however, is not unique. • Most carbon atoms have six neutrons, but they some have seven or even eight neutrons. • However, they are all carbon because they have six protons.

24. Atomic mass • The atomic mass of an atom is the number of protons plus the number of neutrons. It is measured in amu. • So, if carbon has six protons and six neutrons, what is its atomic mass? • 12 amu. • Remember that electrons are so small that their mass is insignificant. • Therefore, only the protons and neutrons in the nucleus matter.

25. Chemical symbols • A chemical symbol is a one or two letter code used to symbolize an element. • What is C? • carbon • What is B? • Boron • What is Be? • A verb. Ha! Beryllium • How about H? • The symbols are often based on the Latin word for the element. For example, iron is Fe.

26. Sum it up… • With your lab partner, review these thoughts- • The nucleus of an atom is made up of what? • The atomic number is the what? • The atomic mass is the what? • What charge does a proton have? • What charge does an electron have? • What charge does a neutron have? • What are electron rings for?

27. The nucleus is made of protons and neutrons. • The atomic number is the number we use to identify the element-as in Elemental Mondays. • The atomic number=number of protons. • The atomic number=number of electrons. • The number of protons=number of electrons. • Atomic mass (will be a large number)-atomic number (will be a small number) =number of neutrons. • The electron rings hold electrons. • The protons determine the element, but the electrons determine the chemical reaction.

28. Now, apply what you have learned… • With your lab partner, I want you to fill out all the information you can about an element-mass, number, number of protons, etc. • You get to pick the element. • The catch-no technology. Use your brain. • Be ready to present also.

29. posttest • Let’s try the pretest again. • #1 What is the chemical symbol for iron? • Fe • #2 Sodium (Na-atomic number 11) is an element that is found in table salt. Explain how many electrons are in a neutral atom of sodium. • If the atomic number is 11, then the number of electrons is 11. The atomic weight is the number of protons. Protons = electrons.

30. Posttest • #3 Which atomic particle is positively charged? • The proton is positive; the electron is negative; the neutron is neutral. • #4 You are an electron involved in chemical reactions. Where are you found? • You are found in the electron cloud in the last energy level. • #5 What is the atomic number of an atom that contains 26 protons, 29 neutrons, and 26 electrons? How do you know? • The atomic number is the number of protons. Therefore, the atomic number is 26. • Bonus! What element is it? • It is iron.

31. Let’s Start with a lab • Is it magic, or is it science? • Let’s see. • What you will need- • Water • A measuring cup • Food coloring • A clear container-a plastic cup • A Sharpie • Rubbing (isopropyl) alcohol • A spoon or other mixing device Don’t get the alcohol in your eyes.

32. The Procedure • Take notes. • You will be combining two liquids. • You will combine one cup of water with one cup of alcohol. • First, let’s form a hypothesis. • The question-How much of the final liquid will you have? • Now, we try it…

33. What you will do- • Carefully measure two cups of water and pour it into the clear cup. • Mark the top of the water. • Pour the water back out. • Pour one cup of water back in. • Mix a few drops of food coloring in the water. • Next, carefully measure one cup of rubbing alcohol. • Pour it into the cup of colored water. • Now, read how much of the final liquid you have. • Prepare your data. • Write your conclusion. • Can you explain what occurred?

34. What happened? • Magic or science? • Science! • When you combined the two liquids, some of the alcohol molecules found their way into the spaces between the water molecules. • What are molecules? • What elements were involved here? • How does this happen? • That is what we are about to learn!