West Germany's parliament unseated Chancellor Helmut Schmidt today and elected conservative leader Helmut Kohl to succeed him, ending 13 years of Social Democratic rule marked by welfare-state policies and the expansion of detente.

A composed Schmidt walked slowly across the floor of the lower house to shake Kohl's hand when the vote was announced: 256 to 235, with four abstentions. It was seven more than Kohl needed and marked the first time in West Germany's 33-year history that a sitting chancellor had been removed by parliament through a so-called constructive vote of no confidence.

Schmidt and his Social Democratic predecessor, Willy Brandt, had pursued a policy of Ostpolitik, expanding West Germany's political contacts and trade with the Soviet Union and its allies while maintaining its key role in the Western alliance. Kohl enters office with a strongly pro-Western stand.

The changeover represents a personal triumph for the 52-year-old Kohl, who becomes West Germany's sixth chancellor and the youngest to assume the job.

Against widely expressed doubts about his leadership potential, the affable Christian Democratic Party chairman has deftly managed to form a new center-right coalition since the breakup of Schmidt's center-left government two weeks ago. But it is still a very unsettled partnership, hampered by open strains between the arch-conservative Bavarian wing of the Christian Democratic Union and the liberal Free Democratic Party which deserted Schmidt's government.

In a fighting farewell address before the vote, Schmidt, still the country's most popular politician, bitterly accused his opponents of undermining confidence in West Germany's democratic institutions by bringing him down without a mandate.

Charging his erstwhile Free Democratic partners with offering only "very threadbare" explanations for switching sides, he said, glancing at their party leader, his former foreign minister Hans-Dietrich Genscher: "For many years, Mr. colleague Genscher, the people will not forget this behavior."

"Your actions are legal," Schmidt declared, "but they have no inner moral justification."

Genscher, who will reassume the post of foreign minister, and Kohl have promised new elections next March. But Schmidt echoed rising speculation that the new coalition will find some excuse to avoid a vote that threatens to eliminate the Free Democrats from parliament.

Saying he doubted the honesty of the new election pledge, Schmidt said caustically, "It was of course intended to calm down upset voters. And your untrue slogan about a state of emergency is only to divert attention from the fact that you do not wish immediate new elections." The ex-chancellor had called for new elections before the year's end, and noted today that three-fourths of the country backed him, according to snap surveys.

Citing the accomplishments of his party's 13 years in power, including his own 8 1/2 years as chancellor, the 63-year-old Schmidt warned Bonn's new leadership not to reverse the political reputation that was built up for West Germany abroad or the social welfare advanced at home.

Opposition leaders defended what they were about to do against Schmidt as a legitimate exercise of a constitutional provision by elected representatives of the people. They said the years of Social Democratic rule had reached a dead end.

Kohl, beaming with satisfaction after the vote, told reporters the immediate priority of his government would be to attack the rising unemployment and revive the economy. Asked how best to describe his future politics, he replied, "I would like a government and a policy of the center for the Federal Republic."

"This means," he went on, "we must make sure that no new animosities are created in this country, and we must see our purpose not [in] doing as much as possible against each other but in finding our way toward each other as much as possible."

But more so than in a hard-fought election campaign, this change of power has left deep scars between West Germany's parties and lingering questions in the public mind over the way it came about.

The new government partners still seem far apart on some important issues of domestic policy, and officials in all parties have expressed the view that a conservative-led Bonn government could result in greater polarization -- between left and right, employers and workers, Germans and foreigners -- in the country.

Badly splintered by its swing to the right, the Free Democratic Party itself faces possible extinction. Two of its members who held senior posts in Schmidt's coalition -- former interior minister Gerhart Baum and former minister of state Hildegard Hamm-Bruecher -- rose today to object to Schmidt's ousting in speeches vigorously applauded by the Social Democrats.

"Helmut Schmidt -- to be brought down without a voters' verdict! Helmut Kohl -- to reach the chancellorship without a vote! I feel this has the odium of violated democratic decency," Hamm-Bruecher declared indignantly. "It damages the moral and ethical integrity of changes of power."

Agitated by the charge they were doing something immoral, Heiner Geissler, secretary general of the Christian Democrats, heatedly accused critics of launching "an attack on our constitution."

This brought an angry Schmidt back to the podium. Banging his fist and shouting, "I still have the right to speak here," to overcome hecklers, he said:

"If the free expression of opinion of a member of parliament who says that she would like to speak and act according to her conscience is called an attack on our constitution, then the leadership of the Free Democratic Party should ask itself whether it really wants to forge an alliance with such illiberality and intolerance."

Kohl, who had not intended to speak before the vote, tried to calm the assembly by cautioning against hasty words. "Let us not in the passion of the hour destroy what this republic has built up on our constitution in 30 years," he advised.

But Schmidt asserted that "this change of government that you are attempting affects the credibility of our democratic institutions."

German experts have differed over whether the way Kohl plans to call new elections -- by asking for and deliberately losing a vote of confidence in parliament next January -- is legal. Some contend it would be a manipulation of the constitution, given Kohl's clearcut majority today, to pretend he had none in order to force new elections. But senior conservative politicians assured today that new elections would be sought as promised.

Going on to rip apart Kohl's policy program, agreed on this week, Schmidt warned that the "deflationary politics" of the new government would lead, after a brief illusionary boom, to more unemployment, like in the United States.

He alleged that new burdens would fall on those who could least afford it -- tenants deprived of tough old rent controls, students robbed of aid, large families denied state child support, pensioners facing postponed payments and welfare recipients deprived of new assistance. Schmidt spoke of a forthcoming "redistribution from bottom to top."

"We Social Democrats," he stated, "will oppose every attempt to repress social justice . . ."

On foreign policy points, he urged Kohl to use and expand West Germany's existing contracts with the East Bloc, not to break off the dialogue with East Germany and to continue to pressure the United States and Soviet Union to disarm through negotiations.

The job of answering Schmidt and formally presenting the no-confidence motion fell to the eloquent Rainer Barzel, the former Christian Democratic party chairman who failed 10 years ago to unseat Schmidt's predecessor, Brandt -- the only previous occasion a no-confidence vote had been tried in West Germany.

Barzel assured that the new government was "cautious, experienced and peaceable enough" to avoid war. But, striking the strong pro-West tone that is expected from the Kohl coalition, Barzel declared, "Our place is not between East and West. It is only from the West, and in the West, that we can have effect on balance.

"With both feet firmly in the West, we want to reach out our hand to the East," he said.

In Washington, White House Deputy Press Secretary Mort Allin said the United States had "worked very closely with all postwar (West German) governments and we anticipate we will continue to do that." The Soviet Union made no immediate comment on the changeover, but officials in Moscow have made clear that the Kremlin is concerned, Reuter reported.

Barzel charged that the Social Democrats had become incapable of governing, leaving behind a plundered state cashbox and mass unemployment. Bickering, too, within the party over support for NATO policy had caused West Germany's allies to start asking, "What is wrong with the Germans?" he said.

He told Schmidt that critics in the chancellor's own party brought him down: "None of us has spoken about you as insultingly and contemptuously as some of your fellow party members.".

Despite the day's fierce political bashing and ill feeling, it did have its moments of dignity and sad parting befitting the passing of an era. Schmidt's warm expressions of lasting regard for at least some Free Democratic Party members was returned in a moving statement by the party's floor leader, Wolfgang Mischnick.

The chancellor's official leave-taking, administered by President Karl Carstens in his Villa Hammerschmidt residence, was a brief, solemn ceremony, as was Kohl's swearing-in shortly thereafter in the same place.

As a final official act, Schmidt traveled to the Defense Ministry grounds for a military parade of honor he had requested, having served earlier as defense minister. He kept a disciplined grip on his emotions throughout the day, looking downcast but calm.