For example graphite.
Native element minerals
The atomicity of an element refers to the number of atoms present in a single molecule of that element. For example, oxygen has an atomicity of 2 because its molecule contains 2 oxygen atoms (O2), while helium has an atomicity of 1 since it exists as single atoms (He).
All atoms of any single element have the same number of protons and electrons.
Probably the diamond, which is pure Carbon. I don't know offhand if its the only single element gemstone.
A pure element contains one sort of atoms, and all the elements have the same number of protons (which define the element). But the atoms can have different masses, so called "isotopes" (see link). Thus, chemically there is only one kind of atoms in a pure element, but there can be several physically different kinds of nuclei in a pure element.
This is a single displacement reaction.
No, malachite is not an element. Malachite is a mineral that is composed of copper, carbon, and oxygen atoms.
Magnesium atoms have 12 electrons.
atoms
The element that contains 14 protons in its atoms has the atomic number 14. On the Periodic Table, this element is silicon, Si.
Rutherfordium is a single chemical element.
Yes, graphite is a non-silicate mineral. It is composed of carbon atoms arranged in a hexagonal crystal structure, making it a native element mineral rather than a silicate mineral which contains silicon and oxygen.