Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Thayer Jonathan W
   2. Issuer Name and Ticker or Trading Symbol
EXELON CORP [EXC] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
EVP and CFO as of 3/12/2012
(Last)
(First)
(Middle)
10 SOUTH DEARBORN STREET, 54TH FLOOR		 3. Date of Earliest Transaction (Month/Day/Year)
03/12/2012
(Street)

CHICAGO, IL 60603		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 03/12/2012   A   22,770 A (1) 22,770 D  
Common Stock- 401k Plan Shares 03/12/2012   A   1,459 A (2) 1,459 I by 401k Plan
Common Stock 03/12/2012   A   669 A (1) 669 I Trust for daughter
Common Stock 03/12/2012   A   669 A (1) 669 I Trust for son

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
NQ Stock Options 01/02/2003 $ 30.26 03/12/2012   A   13,020     (3)   (3) Common stock 13,020 (3) 13,020 D  
NQ Stock Options 05/02/2003 $ 30.98 03/12/2012   A   5,542     (3)   (3) Common stock 5,542 (3) 5,542 D  
NQ Stock Options 02/26/2004 $ 42.62 03/12/2012   A   5,319     (3)   (3) Common Stock 5,319 (3) 5,319 D  
NQ Stock Options 02/24/2005 $ 54.8 03/12/2012   A   5,487     (3)   (3) Common stock 5,487 (3) 5,487 D  
NQ Stock Options 02/22/2007 $ 81.56 03/12/2012   A   8,342     (3)   (3) Common stock 8,342 (3) 8,342 D  
NQ Stock Options 02/21/2008 $ 101.05 03/12/2012   A   8,676     (3)   (3) Common stock 8,676 (3) 8,676 D  
NQ Stock Options 02/27/2009 $ 21.25 03/12/2012   A   167,669     (3)   (3) Common Stock 167,669 (3) 167,669 D  
NQ Stock Options 02/26/2010 $ 37.71 03/12/2012   A   67,304     (3)   (3) Common stock 67,304 (3) 67,304 D  
NQ Stock Options 02/25/2011 $ 32.46 03/12/2012   A   125,429     (3)   (3) Common stock 125,429 (3) 125,429 D  
NQ Stock Options 02/24/2012 $ 39.24 03/12/2012   A   175,946     (4)   (4) Common stock 175,946 (4) 175,946 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Thayer Jonathan W
10 SOUTH DEARBORN STREET
54TH FLOOR
CHICAGO, IL 60603		       EVP and CFO as of 3/12/2012  

Signatures

 Scott N. Peters, Attorney in Fact for Jonathan W. Thayer   03/14/2012
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Common stock acquired pursuant to the Agreement and Plan of Merger (the "Merger") between Exelon Corporation ("Exelon"), Bolt Acquisition Corporation and Constellation Energy Group, Inc. ("Constellation"), whereby each share of Constellation common stock was converted to 0.93 share of Exelon common stock and a cash payment being made for any fractional shares.
(2) Common stock held in a multi-fund 401(k) plan, acquired pursuant to the Merger, whereby each share of Constellation common stock was converted to 0.93 share of Exelon common stock and a cash payment being made for any fractional shares.
(3) Non qualified employee stock options originally granted by Constellation that vested and were converted pursuant to the Merger. Each Constellation option was converted into an option to purchase Exelon common stock at the rate of 0.93 shares of Exelon common stock for each share of Constellation common stock at a strike price equal to the quotient of the original Constellation strike price and 0.93.
(4) Non qualified employee stock options originally granted by Constellation that were converted pursuant to the Merger. Each Constellation option was converted into an option to purchase Exelon common stock at the rate of 0.93 shares of Exelon common stock for each share of Constellation common stock at a strike price equal to the quotient of the original Constellation strike price and 0.93. These stock options were granted on 2/24/12 and 1/3 will vest on each of 2/24/13, 2/24/14, and 2/24/15.

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