Elements & Atoms
An atom refresher Matter is anything that takes up space and has mass. All matter is made of atoms Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses.
An atom refresher An atom has three parts: Proton = positive Neutron = no charge Electron = negative The proton & neutron are found in the center of the atom, a place called the nucleus. The electrons orbit the nucleus. Picture from http://education.jlab.org/qa/atom_model_03.gif
Atomic Theory Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements Two or more different atoms bond in simple ratios to form compounds, such H 2 O, CO and Fe 2 O 3 How Small Are Atoms? 4
Subatomic Particles Particle Symbol Charge Relative Mass Electron e - - 0 Proton p + + 1 Neutron n 0 1 5
What are elements? Elements are the alphabet to the language of molecules. To make molecules, you must have elements. Elements are made of atoms. While the atoms may have different weights and organization, they are all built in the same way. Information & picture from Chem4kids at http://www.chem4kids.com/files/atom_structure.html
Graphic from http://education.jlab.org/atomtour/fact2.html
More about Elements.. Elements are the building blocks of all matter. The periodic table is a list of all of the elements that can build matter. It s a little like the alphabet of chemistry. The periodic table tells us several things
Periodic Table Atomic Number: Number of protons and it is also the number of electrons in an atom of an element. Element s Symbol: An abbreviation for the element. Elements Name Atomic Mass/Weight: Number of protons + neutrons. 8 O Oxygen 16
Elements on the Periodic Table Atomic Number Symbol Atomic Mass 11 Na 23 10
An Element's Symbol Each element has a unique symbol One or two letters First letter is always capitalized Second letter is always in lower case letters C = carbon Ca = calcium O = oxygen Co = cobalt Fe = iron Zn = zinc 11
Atomic Number Counts the number of protons (+) in an atom 12
All atoms of an element have the same number of protons 11 11 11 11 11 Na Na Na Na Na 11 11 11 11 11 Na Na Na Na Na Every Na (Sodium) atom has 11 protons 13
Learning Check Multiple Choice: Use your periodic table to find out how many protons each element has. 1. Nitrogen a) 5 protons b) 7 protons c) 14 protons 2. Sulfur a) 32 protons b) 16 protons c) 6 protons 3. Barium a) 137 protons b) 81 protons c) 56 protons 14
Solution The number of protons each element has is: 1. Nitrogen b) 7 protons 2. Sulfur b) 16 protons 3. Barium c) 56 protons 15
Mass Number Counts the total number of protons (+) and neutrons (o) in an atom 16
Electrons An atom is neutral The overall net charge is zero Number of protons (+) = Number of electrons (-) So, the atomic number tells us the number of protons as well as the number of electrons 17
Subatomic Particles in Some Common Atoms 8 15 30 O P Zn 16 31 65 8 p + 15 p + 30 p + 8 n 16 n 35 n 8 e - 15 e - 30 e - 18
Learning Check Use your periodic table to write the atomic symbols for atoms with the following: A. 8 p +, 8 n, 8 e - B. 29 p +, 35 n, 29 e - C. 47p +, 60 n, 47 e - 19
Solution 8 O A. 8 p +, 8 n, 8 e - 16 B. 29p +, 35n, 29e - 29 Cu 64 C. 47p +, 60 n, 47 e - 47 Ag 107 20
Practice What is the name for the element with the symbol Na? Sodium What is the atomic number of Hydrogen? 1 What is the atomic mass of Nitrogen (N)? 14.007 **We will talk about the decimals later
Practice Cont. What is the chemical symbol for Mercury? Hg What is the atomic number of Plutonium (Pu)? 94 What is the atomic mass of Gold? 196.966
Atomic Mass Actual atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom. Some periodic tables round the atomic mass number. Isotopes 23
Isotopes There are different versions of elements Atoms have the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) have different mass numbers 2 Isotopes of chlorine 17 Cl 17 Cl 35 37 chlorine - 35 chlorine - 37 24
Learning Check Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 6 C 6 C 6 C 12 13 14 #p #n #e 25
Solution 6 C 6 C 6 C 12 13 14 #p 6 6 6 #n 6 7 8 #e 6 6 6 26
Atom Models There are two models of the atoms we will be using in class. Bohr Model Lewis Dot Structure Created by G.Baker
Bohr Model The Bohr Model shows all of the particles in the atom. - In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. + + - In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. Created by G.Baker
Bohr Diagrams A simple way to diagram atoms Protons and Neutrons are found in the nucleus. Electrons are found orbiting in clouds, called energy levels (or shells), around the nucleus. Each level must be full before electrons can move to the next level. First level can hold only 2 electrons. Each level thereafter can hold 8 electrons. This is called the Octet Rule Atoms without a full outer shell are more likely to react with other atoms. 29
Practice! Oxygen has N, P and E Draw the nucleus. Add P and N Draw the first energy shell Add electrons to fill the first shell Draw the second energy shell Add the remaining electrons. (note that the second shell is not full yet!) 30
The Atom Oxygen 8 Protons 8 Electrons (2 in first energy shell, 6 in outer shell) 8 Neutrons 31
Oxygen has: 8 neutrons 8 protons 8 electrons Note that the outer shell is NOT full, that it could hold 2 more. 32
More Practice! Diagram a Fluorine Atom 33
The Atom Fluorine 9 Protons 9 Electrons (2 in first energy shell, 7 in outer shell) 10 Neutrons 34
Fluorine has: 10 neutrons 9 protons 9 electrons Note that the outer shell is NOT full, that it could hold 1 more. 35
Once More! Diagram a Neon Atom 36
The Atom Neon 10 Protons Electrons (2 in first energy shell, 8 in outer shell) 10 Neutrons 37
Neon has: 10 neutrons 10 protons 10 electrons Note that the outer shell is full. This atom will not react with others. 38
And Again! Diagram a Sodium Atom 39
The Atom Sodium 11 Protons 11 Electrons (2 in first energy shell, 8 in second shell & 1 in outer shell) 12 Neutrons 40
Sodium has: 12 neutrons 11 protons 11 electrons Note that the outer shell is NOT full, that it could hold 7 more. 41
Electrons have special rules. You can t just shove all of the electrons into the first orbit of an electron. Electrons live in something called shells or energy levels. Only so many can be in any certain shell. Created by G.Baker
Nucleus 1 st shell 2 nd shell 3 rd shell Adapted from http://www.sciencespot.net/media/atomsfam.pdf Created by G.Baker
Electrons have special rules. You can t just shove all of the electrons into the first orbit of an electron. Electrons live in something called shells or energy levels. Only so many can be in any certain shell. The electrons in the outer most shell of any element are called valance electrons. Created by G.Baker
So let s try it. How to draw a Lithium atom First, look at the Periodic Table Second, determine the number of protons (Look @ the atomic number) Then determine the number of neutrons (Atomic mass atomic number) Then determine the number of electrons (Look @ the atomic number) 3 Li Lithium 7 Created by G.Baker
So let s try it. Protons = 3-3 + Li - + + - Lithium 7 Electrons = 3 2 in the 1 st shell, 1 in the 2 nd shell Neutrons = 4 (7-3=4) Created by G.Baker
Lewis Dot Structure The Lewis Dot Structure is a bit different from the Bohr model. It only shows the element symbol and it s outer most electron shell. - - - + + + + + + + - - - - + O - Created by G.Baker
How to 1. Write the symbol. 2. Start on the right hand side, working your way clockwise around the symbol. 3. Try Lithium Created by G.Baker
Your activity Using the beans (Lentils are electrons, Lima Beans are protons, and kidney beans are neutrons), create a Bohr model, and then a Lewis dot structure model of each of the first 20 elements. After you have created each model, draw each model on your chart. Hint to make a chart, use a burrito fold, then fold the top down by 1 ½ inches. Unfold, you now have 3 columns. Label the columns: element, Bohr model, Lewis Dot. Created by G.Baker