Chemistry help! Which elements are the unique elements?

[jorganos]

The only unique element in the system is hydrogen, because it doesn't fit into any group. That said, the first ten elements of the periodic system are exceptional, too, because they lack the d-orbitals to enable more electron configurations, but hydrogen also lacks the p-orbitals. (So does helium, but as a noble gas this doesn't matter much.)

[Jacob]

My Teacher gave me a study guide that I'm supposed to study off of and it said "Know the periodic table in terms of Metalloids, Electron arrangements, Noble Gases, UNIQUE ELEMENTS, Metals, Nonmetals, Location, and Properties.

All I want to know is which elements are the Unique Elements, THANKS IN ADVANCE

[Lina]

I guess what your teacher means are knowing about elements which are unique in nature. Here are a few i believe are unique -

1. Hydrogen - Coz it is the only element that doesn't have a neutron. It behaves as a metal as well as a non - metal.

2. Carbon - Coz this element forms more compounds than the rest of elements in the Periodic Table put together.

3. Mercury - Coz it is a metal and yet it is liquid.

4. Gallium - It is a metal, yet it melts in your hand.