Local attorneys John R. Cope, Joseph H. Koonz Jr., and Douglas J. Patton have been elected to the board of directors of Century National Bank, which is scheduled to open early next month.

Joseph B. Gildenhorn has been elected vice chairman of the board of the D.C. National Bancorp and its subsidiary D.C. National Bank. Gildenhorn is a partner in the law firm of Borwn, Gildenhorn & Jacobs.

Ruth S. Block and Richard R. West have been elected governors at-large of the National Association of Securities Dealers Inc. Block is executive vice president of Equitable Life Assurance Society of America and West is dean of the Dartmouth College Amos Tuck School of Business Administration.

Linda J. Fillingham has been named executive vice president and chief operating officer of Friendship Savings & Loan of Chevy Chase. In addition, Joan Neale Spermo has become executive vice president of Friendship Services Inc., a subsidiary of the S&L.

Linden E. Wheeler has become a director of Credit Card Service Corp. He was formerly in charge of the domestic and foreign credit operations of Sears, Roebuck & Co.

Valerie Morse Riggins has been promoted to government relations director of Beneficial Management Corp. of America.

Susan G. Riel has been promoted to senior vice president in charge of personnel and bank administration for Security National Bank.

V.A. Sweeney, president of Suburban Savings and Loan in Annandale, has been appointed chairman of the 1982 management committee of the U.S. League of Savings Associations.