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.