Answer: A neutral Phosphorus Atom has five valence electrons. These are contained in the third energy level of the atom.

• How Many Phosphorus Valence Electrons

A way to find valence electrons without the periodic table is using the atomic number and drawing a diagram. The atomic number is how many protons and electrons the atom has. That means an atomic number of 8 (oxygen), has 8 protons and 8 electrons. Valence electrons are kind of like the directions to a Lego set. In this lesson, we will learn what valence electrons are and why scientists need to know the number of valence electrons an atom has. How many valence electrons are in an atom of phosphorus? (atomic number 15) a. How many electrons does barium have to give up to achive a noble-gas electron configuration? Which of the following elements does NOT form an ion with a charge of 1+? What is the valence shell for a phosphorus atom and how many valence electrons does an atom of phosphorus have? Valence shell = 5, valence electrons = 15 B. Valence shell = 3, valence electronias 3 C. Valence shell = 3, Valence electrons = 5 O D.

The Phosphorus Element as it would be represented on a modern periodic table. Source

Phosphorus is an element which is part of Group 15 (formally known as the Pnictogen group) and is directly below the nitrogen atom. As was mentioned before, a neutral Phosphorus Atom contains five valence electrons in the third shell. You can see a Bohr Model of Phosphorus below this paragraph. It also supports the original answer of five valence electrons.

Bohr Model of a Phosphorus Atom.

Due to the number of valence electrons, Phosphorus is capable of forming three bonds with other elements. Yet since it has a third-energy level, it can form more than three bonds if it is favorable to do so. Phosphorus tends to form an anion even though it has a low electronegativity. Due to its high reactivity, phosphorus is never found a pure element on earth.

Electron Configuration of Phosphorus with a Lewis Diagram on the side as well. Source

The Valence Electrons are found in different types of orbitals. Two are in the s-orbital (a circular orbital) while the other 3 are in p-orbitals (bell-shaped orbitals). There are a total of 4 orbitals in the valence shell to minimize electron-electron repulsion. Since their is less electron-electron repulsion, this formation is actually more stable than one with an extra electron. Therefore Phosphorus has a higher ionization than its Group-16 (Chalcogen) neighbors Sulfur.

Phosphorus as it moves in a biochemical process. Source

Phosphorus is necessary for some functions in life and is an essential component of fertile soil. It moves as a compound (not as a pure element) through what is called the Phosphorus cycle from the soil to plants and then back into the air before returning to the soil. Phosphorus is also essential component of matches. It was discovered in 1669 by Hening Brand.
Sources:
http://thechemistryguru.com/phosphorus/

How Many Phosphorus Valence Electrons