The Big House is so arranged that kindred elements live one above the other off each stair well, comprising the groups and subgroups of the Periodic System. This is the law for the inhabitants of the Big House. By falling into Group I, hydrogen inevitably breaks this law. But where is poor hydrogen to go? There are all in all nine groups, nine stair wells in the Big House. Helium, hydrogen's first-floor neighbour, found its flat only in what is now called the zero group. The places in the rest of the groups are vacant. See how many possibilities there are for replanning the first floor to find hydrogen a real place under the sun!"

   Couldn't it be lodged in the second group, with the alkaline-earth metals headed by beryllium? No, they feel absolutely no kinship towards hydrogen. The third, fourth, fifth and sixth groups also refuse to have anything to do with it. What about the seventh group? Wait! The halogens occupying this group, fluorine, chlorine, bromine, etc., are ready to extend a friendly hand to hydrogen.

   Imagine a meeting between two children. "How old are you?" "So much." "So am I." "I've got a bicycle!" "Me too!" "What's your Dad?" "A truck driver!" "Whee - so is mine!" "Let's be friends?" "Let's!"

   "Are you a non-metal?" fluorine asks hydrogen. "Yes!" "Are you a gas?" "That's right." "So are we," says fluorine, nodding at chlorine. "My molecule consists of two atoms!" contributes hydrogen.

   "Well, what do you know about that!" says fluorine in surprise. "Just like ours. And can you show negative valence, accept additional electrons? We are awfully fond of doing that!"

   "Of course I can. I form hydrogen compounds known as hydrides with the very alkali metals that dislike me so, and my valence in them is minus one."

   "All right then, pitch right in with us and let's be friends!"

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