PALO ALTO -- Mark Zuckerberg said Tuesday he is donating nearly $500 million in Facebook stock to the Silicon Valley Community Foundation, the largest single gift in the history of the local nonprofit and one of the biggest philanthropic donations in the Bay Area this year.

The 28-year-old multibillionaire announced the donation on his personal Facebook page, saying he and his wife want to focus their giving on "education and health." The news drew immediate praise from a local philanthropy expert, who said he hoped Zuckerberg's gift will set a standard for charity among younger tech entrepreneurs who aren't always known for their giving.

"This is a big deal," said Kirk O. Hanson, executive director of the Markkula Center for Applied Ethics at Santa Clara University. "There has been some discussion within the community that the next generation may not be as involved in philanthropy, so it is very important and very symbolic that he has made this commitment."

In a statement, foundation CEO Emmett Carson said, "Mark's generous gift will change lives and inspire others in Silicon Valley and around the globe to give back and make the world a better place." Neither Zuckerberg nor the foundation would describe in more detail how the money will be used.

The foundation, which before Tuesday had about $2 billion in assets, makes grants to a variety of charities that serve the needy locally and around the world. It also assists wealthy donors by advising them on philanthropy, managing their charitable funds and making grants based on their input.

Zuckerberg previously tapped the foundation to handle his pledge to give $100 million over five years to improve public schools in the impoverished city of Newark, N.J., which he announced in 2010 just two months after meeting that city's charismatic mayor, Cory Booker. Zuckerberg funded his Newark pledge by donating stock to the foundation.

Writing on his Facebook page late Tuesday afternoon, Zuckerberg noted that he and his wife Priscilla had pledged two years ago to donate over half their wealth to charity, by joining the so-called "Giving Pledge" campaign promoted by billionaires Bill Gates and Warren Buffett. The pledge doesn't set a timetable but asks wealthy executives to commit to giving over their lifetimes.

The Newark grant was "our first major project," Zuckerberg wrote, adding, "I'm really proud of the work we've done there" in helping New Jersey leaders open new schools and negotiate a better contract for teachers.

"Today, in order to lay the foundation for new projects, we've made a contribution of 18 million Facebook shares to the Silicon Valley Community Foundation," Zuckerberg continued. "Together, we will look for areas in education and health to focus on next. I'm hopeful we'll be able to have as positive an impact in our next set of projects."

As the largest shareholder in his own company, Zuckerberg still owns about $11 billion worth of Facebook stock, whose value has improved in recent weeks after falling steeply last summer in the wake of a much-hyped initial public offering. Facebook reported Zuckerberg's donation in a regulatory filing on Tuesday, but a spokesman declined further comment.

Zuckerberg's gift to the Mountain View-based community foundation is roughly four times the $123 million in grants the foundation says it awarded to nonprofits around the Bay Area last year. But if the foundation follows its usual practice, it's unlikely to distribute all of Zuckerberg's gift in a single year. All told, the foundation manages about 1,600 charitable accounts on behalf of individuals and families that use its services.

While some of Silicon Valley's wealthiest executives -- such as William Hewlett and David Packard -- created their own foundations to distribute their wealth, others who channeled funds through the community foundation include former eBay (EBAY) President Jeff Skoll, who announced in 2005 that he had donated $150 million each to his own private foundation and to a fund affiliated with a forerunner to the community foundation.

But Hanson said many wealthy entrepreneurs wait until later in their lives to make sizable donations. "It's significant that Zuckerberg is young and he is helping develop a culture of giving among younger Internet entrepreneurs like himself," said Hanson.

Zuckerberg's many Facebook friends agreed. By Tuesday evening, more than 90,000 people had clicked the "Like" button on his announcement.

Contact Brandon Bailey at 408-920-5022. Follow him at Twitter.com/BrandonBailey