Do Now: Take out completed homework #1 Take out Atoms Book
Review before the quiz _____1) Bohr’s model of the atom says that electrons a) are mixed in evenly with positive charge b) are found orbiting a positively-charged nucleus c) are found orbiting a positively-charged nucleus in energy levels (shells) d) are found in regions of probability around the nucleus called orbitals
Review Before the Quiz _____5) Dalton’s model of the atom states that atoms e) have positive particles called protons and negative particles called electrons f) have a positively-charged nucleus g) have a positively-charged nucleus with electrons in energy levels (shells) h) are hard solid indivisible spheres
Review Before the Quiz One model of the atom states that atoms are tiny particles composed of a uniform mixture of positive and negative charges. Scientists conducted an experiment where alpha particles were aimed at a thin layer of gold atoms. Most of the alpha particles passed directly through the gold atoms. A few alpha particles were deflected from their straight-line paths. (This question was taken directly from a Regents Exam).
Review before the quiz Most of the alpha particles passed directly through the gold atoms undisturbed. What does this evidence suggest about the structure of gold atoms? Atoms are mostly empty space
Review before the quiz A few of the alpha particles were deflected. What does this evidence suggest about the structure of the gold atoms? The nucleus must be positive since it deflects positively charged alpha particles
Quiz-E-Poo time 12.5 minutes Can use your notes/atom book. Turn ALL OF IT IN when you are done Atom Book Homework Quiz
Where are electrons found in the electron cloud? Bohr was the first to propose that the electrons were located in energy levels A lower case “n” is used to denote these principle energy levels (also called principle quantum numbers). The level closest to the nucleus is labeled n = 1. The next level is labeled n = 2 and so forth.
Where are electrons found in the electron cloud? Each principle energy level had a certain energy value associated with the level. The closer the level was to the nucleus, the lower the energy of the level.
Where are electrons found in the electron cloud? The farther away from the nucleus, the higher the energy of that level. As long as the electrons were in these levels, the electrons do not give off energy.
Number the principle Energy levels
Sidebar: How did he figure that out? Excited Electrons Viewed what the spectrum produced was: Demo:
2. Electron Configuration and the Periodic Table Each principle energy level can only hold so many electrons before the level is full. A quick and easy way to determine the maximum number of electrons (max e - ) that a principle energy level can hold is given by the following:
max e - = 2 n 2. max e - = 2 n 2. First square the principle energy level number (n) then multiply by 2
2n 2 Trick Principle Energy Level (n) Maximum Electrons
Electron Configuration Electrons are arranged around the nucleus by filling up the first principle energy level (n=1), then the second energy level, etc. This is the electron configuration given on your periodic table.
Electron Configuration The number of electrons are listed for each level with a dash between levels: for oxygen (O) which has a total of 8 electrons, the configuration is 2–6
Electron Configuration 2 electrons are located in the first principle energy level 6 electrons are located in the second principle energy level.
Look up the electron config. on the PT for the element given & fill in the chart. Elementn = 1n = 2n = 3n = 4 Ca2882 Na F B
Look up the electron config. on the PT for the element given & fill in the chart. Elementn = 1n = 2n = 3n = 4 Al C H
Side Bar: Look up # 72 Hf What does the ** mean? So the electron configuration of Hf is….. What is the electron configuration of gold (Au) # 79?
Completely Filled vs. Occupied Principle Energy Levels Is this room occupied? Are all the seats completely filled?
Completely Filled vs. Occupied Principle Energy Levels Occupied means that there is at least one electron in the Principle Energy Levels (PEL) Li: 2 – 1 has 2 occupied PELs
Completely Filled vs. Occupied Principle Energy Levels Completely Filled means that each level has its maximum number of electrons which can be determined by the 2n 2 rule. n =1 then 2(1) 2 =2 & n = 2 then 2(2) 2 =8 Li: 2 – 1 has only 1 Completely Filled PEL
To help you review the 2n 2 rule complete the following chart PEL (n) Max e
In the chart: Copy the electron configuration from the Periodic Table Determine the number of Occupied Principle Energy Levels (PEL) Determine the number of Completely Filled Principle Energy Levels
Max e - : Elemen t Electron Conf.# ocup p # compl filled C
Max e - : Elemen t Electron Conf.# ocup p # compl filled Na O Cl
Max e - : Elemen t Electron Conf.# ocup p # compl filled He F Ne
Max e - : Elemen t Electron Conf.# ocup p # compl filled Si Zn Au
3. Drawing Bohr Diagrams of Atoms: 1) A circle is used for the nucleus- the # protons (# p or +) and the # of neutrons (#n) are placed in the circle. 2) A ring is drawn around the nucleus for each energy level. 3) The electrons for each energy level are placed in pairs symmetrically around the nucleus
For Fluorine (F) atomic # = _________ atomic mass = ______ electron configuration: __________________ _ # p = ______________ # n =_______________
For Aluminum (Al) atomic # = _________ atomic mass = ______ electron configuration: __________________ # p = ______________ # n =_______________
Going Backwards: Determining the identity of an element from the Bohr diagram: # p = _____________ # n =______________ atomic # = _____________ atomic mass = # p + # n = ________________ electron configuration: ___________________ ____ Isotopic Notation:
Going Backwards: Determining the identity of an element from the Bohr diagram: # p = _____________ # n =______________ atomic # = _____________ atomic mass = # p + # n = ________________ electron configuration: ___________________ ____ Isotopic Notation:
To review: To draw a Bohr Model: Look up the atomic #, atomic mass & the electron configuration Determine the # of neutrons (atomic mass- atomic #) Draw nucleus & write the # p & #n in nucleus Draw rings around the nucleus equal to the # of PEL in atom (# of numbers in electron configuration) Place electrons for each level symmetrically in the rings in pairs
Going Backwards writing Isotopic Notation: # of protons = atomic number so look up the atomic # to get symbol Add the # of protons and neutrons to get the atomic mass (mass #) Atomic mass is the top number 10 Ne 20 Atomic # is the bottom number
Now it is your turn! Complete the Bohr Model worksheet. When done, show me and turn in. If not done, it becomes homework along with homework #2.