Halifax Engineering Inc. has moved into its new five-story, 36,000-square-feet headquarters building in Alexandria's Indian Run Industrial Park at 5250 Cherokee Ave. The company formerly leased space at 5390 Cherokee Ave.

The $2.6 million property was developed through the issuance of an industrial revenue bond sponsored by the Fairfax County Economic Development Authority.

Halifax Engineering was founded in 1967. Sales for fiscal year 1983 are reported to approximate $21 million.

Other recent developments in commercial realty in the Washington metropolitan area:

* The law firm of Frederick and McKernon is expanding its present facility at 51 Monroe St. in Rockville and has leased 1,547 square feet of space. The aggregate rental value of the three-year lease is about $75,000.

* Raven Systems Inc. has leased 8,000 square feet of space at 1101 Vermont Ave. NW for its new Washington headquarters. The aggregate rental value of the five-year lease is $1 million.

* The Downtown Jaycees of the District of Columbia have moved to 1140 Connecticut Ave. NW, Suite 295. The Jaycees were formerly located at 733 15th St. NW.

* Confertech International Inc., a telecommunications firm, has leased about 2,600 square feet of space at 1300 N. 17th St. in Arlington.

* The Fred D. Thompson law firm has leased about 2,500 square feet at 1919 Pennsylvania Ave. NW.

* Communications Development Corp., a consulting firm, has leased 2,300 square feet of space at 2828 Pennsylvania Ave. NW.

* Cahner's Publishing Co. has leased 1,300 square feet of space at 1435 G St. NW.

* Myers Candy & Tobacco, a wholesale cash-and-carry service, has leased 5,500 square feet of space at 7601 New Hampshire Ave. in Langley Park. CAPTION: Picture, New $2.6 million headquarters for Halifax Engineering in Alexandria.