With a white lab coat over his school-mandated burgundy shirt and shorts, 11-year-old Henry Worrell admonished his classmates to watch a video presentation closely.

“Please pay attention to the video because the answers will come from that,” he said.

Sternly, he said again, “Pay attention.”

This was Henry’s turn to be the teacher. Each student in his fifth-grade class at Bernard Terrace Elementary had taught a lesson as one of their final assignments, but Henry had budded with excitement for weeks.

Henry wanted to teach about the periodic table of elements, to share one of his great fascinations with the rest of the students, and to introduce the class to one of his favorite authors via the magic of technology.

So he started by playing some entertaining videos and cartoons about the elements, then passed around some of his collection of the elements, some of which were encased in see-through blocks, including a razor-thin strip of 14-karat gold.

“How much is it worth?” Henry said, repeating a question from his classmates. “Probably a few cents.”

“Next we have germanium, named after a country,” he said, passing around another cube encasing a silver-gray clump. “I bet you can guess which one.”

There was a tube of foil, to represent aluminum, a bottle of Pepto Bismol, for bismuth, and a red-orange bowl colored with a glaze containing uranium-oxide.

“He is very passionate about the periodic table,” said his mother, Kendyl Worrell, who snapped photographs from the back of the class.

While his mother and his teacher, Melanie Swindler, collected the samples, Henry introduced his guest, who would appear by Internet connection on the Skype video chat service.

“Theodore Gray is the person who inspired me to do this lesson plan,” he said.

Gray, a columnist for Popular Science, a software designer, author and “populariser of science,” as his online biography phrased it, captured Henry’s imagination years before when Henry became interested in the elements. Gray maintains websites about the periodic table, including a site about his table of the periodic table — a wooden representation of the table with legs and cubbies containing samples of the elements, some of them especially hard to come by.

At 2:30 p.m., Gray’s face and graying beard appeared on the interactive screen at the front of the room, his office wall bookshelf behind him.

“I can hear you. Can you guys hear me?” he said from his home in Illinois.

Henry acted as the mediator, taking questions from the class. He told them about buying samples of hard-to-find elements on eBay, then getting a call from the Federal Bureau of Investigations when he bought an old missile part online.

“What is your favorite element?” asked Ben Saari.

“People like to ask me that,” Gray answered. “I don’t have one. I don’t have a favorite child, either.”

But he does love titanium because it is a strong, light metal, and sodium, because it explodes in bodies of water. He posts videos of such fun experiments regularly.

He brought out samples of his own elements, including a golden-colored bar labeled “2 Kilos.” The class started whispering and gasping.

“This turns out to be completely fake,” he said.

New education standards encourage teachers to use technology with their students, many of whom have been using computers, smartphones and touch screen tablets their entire lives.

“This is something that fifth-graders should be doing on a regular basis,” said Lynn Carmouche, the acting principal of Bernard Terrace Elementary. “These children are so adept at using technology, so they should be using this on a regular basis to make learning more engaging.”

Henry agreed. His mother said that he wanted to make science fun for his classmates since he saw a presentation from a performer named Doktor Kaboom! in December.

“I think by making science fun, kids will like it,” he said. “Right now, it’s just dull.”

A few years ago, Henry’s father told him a story about a Chinese emperor who died after ingesting mercury — he thought it would make him live forever. Henry became incredibly interested in the elements after that. When he was 7, he asked Santa Claus for a Theodore Gray book, and he became even more interested in the elements.

His lesson plan involving Gray took a great deal of planning, but Henry can be very determined, Swindler said.

In the past, Swindler used Skype to contact classes in other states for chats, but had never tried to speak with authors or scientists.

“That’s definitely something I’m going to integrate,” she said.

During the chat with Gray, Julia Connor wondered how long he had been doing science.

“Since I was a child,” he said. “Most kids are doing science all the time, because that’s how they find out about the world.”

“Doing science” included making gunpowder as a kid and throwing sodium in a lake.

They asked questions until the Internet connection died, then reconnected.

When it disconnected again a few minutes later, the class was disappointed. They had planned to thank Gray for his time.

“Should I stop?” Henry asked Swindler.

“It’s your lesson,” she replied from the rear of the room.

Henry stood with his hands in his lab coat’s pockets, then asked, “Did you enjoy this lesson?”

“Yeah,” a few in the class said, then followed with applause.