How many secondary (2°) carbons are found in 5-ethyl-3,3,4-trimethylheptane? ?

3 secondary carbons are found in 5-ethyl-3,3,4-trimethylheptane.

Explanation:

5-ethyl-3,3,4-trimethylheptane's structure can be seen in the attached picture, in this structure, each vertex represents one carbon atom.

A secondary carbon is a carbon that is bonded to only 2 other carbon atoms, each secondary carbon is highlighted in blue in the attached picture.

There are three secondary carbon atoms in 5-ethyl-3,3,4-trimethylheptane

Organic compounds are usually made up of long chains of carbon. Carbon has the ability to catenate in organic compounds leading to compounds with infinitely long chains.

When a carbon atom is bonded to a single carbon atom, such carbon atom  is primary(1°). A carbon atom that is bonded to two other carbon atoms is a secondary(2°) carbon atom. A carbon atom that is bonded to three other carbon atoms is a tertiary(3°) carbon atom.

There are three secondary  carbon atoms in 5-ethyl-3,3,4-trimethylheptane as we can see from the image attached to this answer.

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answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).