How many valence electrons does this atom have?

4

Explanation:

The given atomic structure appears to have 2 shells/orbits containing electrons – 2 in the inner orbit and 4 in the outer orbit.

Since valence electrons are the electrons present in the outermost orbit/shell of an atom, their number in the given atom becomes 4. (If the 2nd orbit is the outermost orbit, the number of electrons it contains becomes the number of valence electrons).

Why is the number of valence electrons important?

Atoms are neutral, that contain an equal amount of positive and negative charges. All atoms are not stable. Their stability depends upon the number of electrons in specific orbits,( for eg 2 in the innermost orbit, then 8, 18 and so on.)

Valence electrons are loosely attracted by the nucleus and hence can easily be removed from an atom. The number of valence electrons an atom needs to donate/share/accept becomes its valency.

For elements and compounds to exist, the atoms they contain demand stability – which can only be attained by the loss/gain of these valence electrons.

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a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.