We are all a collection of chemicals. All plants and animals are collections of chemicals. The Earth is a collection of chemicals.

Transcription

1 CHEMISTRY UNIT INTRODUCTION & LESSON ONE Introduction We are all a collection of chemicals. All plants and animals are collections of chemicals. The Earth is a collection of chemicals. To understand how and why changes in substances happen we must study chemistry. Chemistry is the study of the composition of substances and the changes that the substances undergo. 1

2 Introduction Chemistry allows us to understand what things around us are made of and how to use them. Understanding chemistry also allows us to produce new materials. As you study chemistry, you must also study how chemistry related issues affect your life and society as a whole. Introduction You will have to make personal choices in your life. Should I use this chemical? What are the harmful effects it has on people and the environment? Are there other chemicals that are just as effective but safer to use? 2

3 Introduction In society, you will influence public decisions in your community, your province and your country. Should some chemicals such as pesticides be banned from use on lawns? Should the government institute stricter regulations on industry to curb the release of chemicals into the environment? What chemicals are released into the environment? What are their effects? What new chemicals should be allowed to be produced? Introduction In order to function, both at an individual level and as a citizen of society, you must be chemistry literate. You must be able to understand the chemistry behind the issues in order to make an informed decision. 3

4 Atomic Theory Early ideas about atoms: Atomic Theory It has taken scientists a long time to understand the basic structure of an. atom Many scientists have carefully worked together to make known the structure of atoms. John Dalton s theory for the structure of the atom stands fundamentally correct today. His understanding that atoms cannot be broken down, however, has been proven. incorrect 4

5 Atomic Theory subatomic Atoms can be broken down into. particles A subatomic particle is a part of an atom much the same as a wheel is part of a car. The three main subatomic particles are,, and. neutrons electrons protons Today, scientists know subatomic particles in turn can be broken down into still smaller. particles Atomic Theory Bohr The model of the atom suggested that travel electrons in a circular orbit or energy in level a welldefined path. Scientists have done experiments to show that this is not the path electrons actually travel. complicated Electron location and movement is more than Bohr thought; however, the planetary model of the atom is used because it is easier to understand and is adequate for a beginning course in chemistry. 5

6 Structure of the Atom modern theory atomic The states that an atom consists of: Protons nucleus located in the of the atom. Protons have a positive charge and have a mass of one atomic mass unit (u). This means that 1u is equal to the mass of a proton. Structure of the Atom Neutrons are also located in the nucleus of the atom. Neutrons have no electrical and charge have a mass of approximately. 1u Electrons are located around the nucleus in less well-defined than orbits first thought. Electrons have a single negative electrical charge but their mass is considered zero since it is so small (approximately 1/2000 the mass of a proton). atom nucleus An consists of a dense surrounded by electrons moving in space. 6

7 Nucleus protons neutrons A nucleus is made of and. 1u Protons and neutrons both have a mass of. The total mass of the atom is equal to the sum of the masses of the protons and neutrons in the nucleus. Nucleus Another interesting thing to note is the difference between the size of the nucleus and the rest of the atom. If an atom were the size of a stadium, football the nucleus would be the size of a. The atomic of an atom is to the number of protons in the nucleus. equal number mass football The atomic is equal to the sum of the number of protons and neutrons. The atomic mass is expressed in atomic mass units (u). 7

8 Electrons Electrons move around the nucleus in specific paths called. Energy levels Energy levels exist whether there is an electron in them or not. Electrons occupy certain energy levels depending on the. atom For example, hydrogen has a single electron in the first energy level. Sodium has two electrons in the first energy level, eight electrons in the second energy level and one electron in the third energy level. Electrons two An atom can have a maximum of electrons occupying the first energy level, eight in the second energy level and in eight the third energy level. We will not study the structure of atoms with more than levels three of energy levels. Each energy level must be before filled electrons occupy the next one. 8

9 Electrons Electrons are so light they are considered to have mass. zero negative Electrons have a electric charge ( ). -1 Fill in the following table: Charge Location (inside or outside nucleus) Mass Protons Electrons Neutrons +1 Nucleus -1 Outside nucleus 0 Nucleus 1u 0 1u 9

10 Periods Alkaline Earth Metals Chalcogens Halogens Nobel Gases 11/2/2017 Alkali Metals I Group II Group Indicates # of valence electrons Non-metals III IV V VI VII VIII These steps divide metals from non-metals The Periodic Table Before going any further we need to reintroduce and review the Periodic Table. The elements are arranged in order of increasing atomic numbers and by placing elements with similar chemical properties in the same column or. group 10

11 The Periodic Table Check out this interactive periodic table at: The periodic table is an important tool for chemists. It quickly determines some key facts about an element. An example entry of an element in the periodic table is shown below. The Periodic Table For the element nitrogen, we see that the atomic number is. 7 This indicates that there are 7 protons in the nucleus of every nitrogen atom. Also, the atomic number provides the number of electrons outside the nucleus. 11

12 The Periodic Table Complete the information for aluminum in the form below. Use a periodic table to find the information. Note: the symbols first letter is always capitalized 13 Al

13 The Periodic Table Periodic tables arrange the elements in columns. A single column is called a group or. family A family contains elements that have similar but not identical chemical properties. The columns are numbered across the top. Some periodic tables use regular number from 1 to 18 to number these columns. Other periodic tables use Roman numerals. Rows in periods Rows in the periodic table are called. Elements in periods do not demonstrate similar properties as they do in families. Periods, however, show. trends There is also a relationship between the period number and the number of or orbits energy levels around the nucleus of the atom. For example, carbon is in the second period and has electrons in 2 energy levels. Calcium is in the fourth period and has electrons in energy levels. 4 13

14 Family Alkali metals Alkaline earth metal Chalcogens Halogens Noble gases Number of valence electrons Group Number I A II A VI A VII A VIII A You will notice that a relationship exists between the group number and the number of electrons. valence The relationship is that the group number equals the number of valence electrons. It is because atoms have the same number of valence electrons that they are placed together in the same group. 14

15 How do atoms of different elements differ from each other? protons neutrons All atoms are made of,, and electrons (i.e., a proton in a carbon atom is the same as a proton in an oxygen atom). The same is true for electrons and neutrons. How do atoms of different elements differ from each other? What determines the difference between atoms of different elements if they are all made of the same subatomic materials? The answer is that atoms of different have elements different of numbers protons in the and nucleus electrons the nucleus. around 15

16 Atomic Number & Mass Number protons The atomic number is equal to the number of in the nucleus. The atomic number is special because it can be used to any known. element identify For example: Carbon has an atomic number of ; oxygen has an atomic number of, 8 and so on. The atomic number of any element is found in the. periodic 6 table Atomic Number & Mass Number mass number All atoms have a. The mass number is equal to the number of plus protons the number of neutrons (e.g., carbon has six protons and six neutrons). The mass number for carbon would be (protons) + 6 (neutrons) = The atomic mass of an atom is expressed in atomic mass units(u). This means the atomic mass of carbon is expressed as. 12u 16

17 Referring to your periodic table, fill in the blanks: Iron ( ) Krypton ( ) Hydrogen ( ) Sodium ( ) Fe Kr H Na Atomic Number Number of Protons Referring to your periodic table, fill in the blanks: Number of Protons Number of Neutrons Lithium ( ) Chlorine ( ) Copper ( ) Silver ( ) Li Cl Cu Ag Mass number

18 Lesson One Exercise #1 Questions 1 & 2 Lesson #1 Worksheet 18