Identifying Elements TEKS: 8.5B - identify that protons determine an element s identity and valence electrons determine its chemical properties, including reactivity. 8.5C interpret the arrangement of the Periodic Table, including groups and periods, to explain how properties are used to classify elements
The Particle Theory of Matter Matter is made of particles that are in constant motion, these particles have space in between them. Every kind of matter is made of one or more elements Atoms are the smallest particle of an element
Elements Elements are the building blocks of all matter An element is a pure substance that cannot be broken down any further and still retain its properties The term 'element' is used to describe atoms with specific characteristics. The periodic table is a graphic organizer of all of the elements
Elements There are currently 118 elements (so far) that have been identified though only 92 of them are naturally occurring.
Identifying Elements Key Questions we will answer: 1. How can we tell atoms apart (at the atomic level)? 2. Why are Protons so important? 3. Why are Electrons so important?
Pages to use: Identifying Elements Outline Page Periodic Table
Think about it - Look at this picture Would you be able to identify the element and the number of protons, neutrons, and electrons? Why or why not?
At first glance you might think, "No, I cannot identify the element because I do not know if the red or green circles are the protons or neutrons, and they are overlapping so I cannot count them."
If you think carefully, you can figure it out. It is easy to identify and count the number of electrons. There are 8 electrons total. If there are 8 electrons, then there are 8 protons.
Eight protons means the atomic number is 8. You can then look on the periodic table to identify the element. What is the element?
On your page, answer this Key Question: 1. How can we tell atoms apart (at the atomic level)? Using the Bohr model, you can count the number of subatomic particles Each element has a specific number of each that identifies it
Identifying Elements Practice: Work with your shoulder partner and a periodic table now to fill in this chart:
Double check your Answers:
2. Why are Protons so important? If you are looking at a Bohr model, you count the protons or electrons to determine the number. The number of protons identifies which element you are looking at. (now write this answer for the second key question)
Understanding PT Organization! The table is organized both horizontally and vertically. The horizontal (across) are called periods The vertical (up and down) are called groups
Periodic Table Label Groups and Periods now! Groups Periods
Make a connection! From our previous lesson, you learn that APE MAN can be used to find the protons, neutrons and electrons using the periodic table. You can also figure out other important information such as valence electrons, element reactivity and more!
3. Why are Electrons so important? Why do we want to know about the electrons, they have so little mass do they really matter? Electrons are important for the bonding of individual atoms together. If electrons didn t bond, none of the substances in our universe would exist! This interaction between the outer electron layers of an atom is called atomic bonding How quickly or even explosively atoms bond is known as the reactivity of an element
Reactivity?? What is this really? Chemical reactivity occurs when substances change chemically. What is most often produced from this type of change is something in the form of energy, such as heat and combustion.
How does the Bohr model help our understanding? The Bohr model shows the Energy levels of an element. In the outer most level, the electrons are called valence electrons. Each energy level can hold a specific number of electrons.
What are energy levels? The first energy level can hold up to 2 electrons and is filled first The second energy level can hold up to 8. The 3 rd can hold up to 18 Many atoms have additional levels: 1st energy level: 2 electrons 2nd: 8 3rd: 18 4th: 32 5th: 50 6th: 72 7th: 98
More on Valence Electrons: There are as many energy levels as the atom needs. The energy level shown furthest from the nucleus is called the outermost energy level. Again, the electrons found here are called valence electrons Different atoms have a different number of valence electrons The group number is equal to the number of valence electrons that an element has (for our purposes)
Video: How to find the number of valence electrons
Valence Electrons and Reactivity When two atoms approach each other and react with each other, it is their outer shells that come into contact first, these electrons in their outer shells that are involved in any chemical reaction. So it is the number of electrons in an atom s outer shell that determines, how that element will react chemically. The periodic table is arranged such that elements in the same column have the same number of electrons in their outer shell.
Octet Rule being stable! 1. Chemical rule that states that atoms of low atomic number tend to combine or become ions (+ or -) so that they each have eight electrons in their valence shell, giving them the same electron configuration as a noble gas (and thus more stability). 2. Having 8 electrons in their outermost shell makes them stable and HAPPY!
Atomic Modeling Practice Bohr Models & Electron Dot Diagrams
Bohr Diagrams how to know how many circles to draw Find out which period (row) your element is in. Elements in the 1 st period have one energy level. Elements in the 2 nd period have two energy levels, and so on. www.chem4kids.com
Bohr Diagrams Practice adding electrons (the dots) 1) Find carbon on the periodic table. 2) Determine the number of electrons it is the same as the atomic number. 3) This is how many electrons you will draw.
Bohr Diagrams putting the circles and dots together! C 1) The C for carbon is done for you and the atom s nucleus is drawn too. 2) Carbon is in the 2 nd period, so it has two energy levels, or shells. 3) Draw the shells around the nucleus.
Bohr Diagrams C 1) Add the electrons. 2) Carbon has 6 electrons. 3) The first shell can only hold 2 electrons.
Bohr Diagrams 1) Since you have 2 electrons already drawn, you need to add 4 more. C 2) These go in the 2 nd shell. 3) Add one at a time - starting on the right side and going counter clock-wise.
Bohr Diagrams C 1) Check your work. 2) You should have 6 total electrons for Carbon. 3) Only two electrons can fit in the 1 st shell. 4) The 2 nd shell can hold up to 8 electrons. 5) But carbon only has 6 total, so this energy level will not be full.
Bohr Diagrams C Try the following elements on your own: a) H b) He c) O d) Al e) Ne f) K
Check your answers fix what you need to! Mistakes are ok learn from them!
Bohr Diagrams H Try the following elements on your own: a) H 1 electron (period 1, group 1) b) He c) O d) Al e) Ne f) K
Bohr Diagrams He Try the following elements on your own: a) H b) He - 2 electrons Period 1, group 8 *the exception c) O d) Al e) Ne f) K
Bohr Diagrams O Try the following elements on your own: a) H b) He c) O - 8 electrons (period 2, group 6) d) Al e) Ne f) K
Bohr Diagrams Al Try the following elements on your own: a) H b) He c) O d) Al - 13 electrons (period 3 energy shells, group 3 valence electrons) e) Ne f) K
Bohr Diagrams Ne Try the following elements on your own: a) H b) He c) O d) Al e) Ne - 10 electrons f) K
Bohr Diagrams K Try the following elements on your own: a) H b) He c) O d) Al e) Ne f) K - 19 electrons
Bohr Diagrams You should now be able to draw a Bohr Model for the first 20 elements in the periodic table. Any Questions?
Electron Dot Diagrams 1) Find Hydrogen on the periodic table. 2) Determine the number of valence electrons. Valence electrons are the number of electrons in the atom s outer most shell. 3) This is how many electrons you will draw.
Electron Dot Diagram Find out which group (column) your element is in. This will tell you the number of valence electrons your element has. You will only draw the valence electrons. www.chem4kids.com
Groups - Review Group 8 = 8 electrons Group 1 = 1 electron Group 2 = 2 electrons Except for He, it has 2 electrons Each column is called a group www.chem4kids.com Each element in a group has the same number of electrons in their outer orbital, also known as shells. The electrons in the outer shell are called valence electrons
Electron Dot Diagram 1) Write the element symbol. 2) Carbon is in the 4 th group, so it has 4 valence electrons. 3) Starting at the right, draw 4 electrons, or dots, counterclockwise around the element symbol.
Electron Dot Diagram 1) Check your work. 2) Using your periodic table, check that Carbon is in the 4 th group. 3) You should have 4 total electrons, or dots, drawn in for Carbon.
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Electron Dot Diagram On your worksheet, try these elements on your own: a) H b) P c) Ca d) Ar e) Cl f) Al
Atomic Modeling You should now be able to draw an electron dot diagram and a Bohr model for the first 20 elements in the periodic table. Any Questions?