How many protons does phosphorus contain?

Atomic number, represented by 𝑍, can be used to distinguish one element from another as each element has its own unique atomic number. When looking at a cell on the periodic table, the atomic number is frequently written above the element symbol. The atomic number also represents the number of protons in the nucleus of all atoms or ions of a particular element. We are told that phosphorus-31 has an atomic number of 15. This means that an atom of phosphorus-31 will have 15 protons.

The question asked us how many neutrons there are in an atom of phosphorus-31. The name phosphorus-31 provides useful information for answering this question. 31 is the mass number of a phosphorus-31 atom. Mass number, represented by a capital 𝐴, indicates the number of nucleons in an atom or ion. Nucleons collectively refer to protons and neutrons. So the mass number can be expressed as the sum of the number of protons and the number of neutrons.

We can use this relationship to determine the number of neutrons in an atom of phosphorus-31. We can substitute the mass number and number of protons into the equation. Then, we can subtract 15 from both sides of the equation to determine that the number of neutrons is 16. Therefore, the number of neutrons in an atom of phosphorus-31 is 16.

For more information on the Visual Elements image see the Uses and properties section below.

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Phosphorus

Discovery date1669 Discovered byHennig Brandt Origin of the nameThe name is derived from the Greek 'phosphoros', meaning bringer of light. AllotropesWhite P, Red P, Black P, P2  

P

Phosphorus

15

30.974  

Glossary

Group
A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.

Period
A horizontal row in the periodic table. The atomic number of each element increases by one, reading from left to right.

Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f).

Atomic number
The number of protons in an atom.

Electron configuration
The arrangements of electrons above the last (closed shell) noble gas.

Melting point
The temperature at which the solid–liquid phase change occurs.

Boiling point
The temperature at which the liquid–gas phase change occurs.

Sublimation
The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.

Density (g cm−3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.

Relative atomic mass
The mass of an atom relative to that of carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists, the value given is the abundance weighted average.

Isotopes
Atoms of the same element with different numbers of neutrons.

CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems.

Fact box

Fact box

Group15 Melting point44.15°C, 111.47°F, 317.3 K Period3 Boiling point280.5°C, 536.9°F, 553.7 K Blockp Density (g cm−3)1.823 (white) Atomic number15 Relative atomic mass30.974  State at 20°CSolid Key isotopes31P Electron configuration[Ne] 3s23p3 CAS number7723-14-0 ChemSpider ID4575369ChemSpider is a free chemical structure database

Glossary

Image explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.

Appearance

The description of the element in its natural form.

Biological role

The role of the element in humans, animals and plants.

Natural abundance

Where the element is most commonly found in nature, and how it is sourced commercially.

Uses and properties

Uses and properties

Image explanation

The image is of a ball-and-stick model of white phosphorus. It has a tetrahedral shape and has the formula P4.

Appearance

The two main forms of phosphorus are white phosphorus and red phosphorus. White phosphorus is a poisonous waxy solid and contact with skin can cause severe burns. It glows in the dark and is spontaneously flammable when exposed to air. Red phosphorus is an amorphous non-toxic solid.

Uses

White phosphorus is used in flares and incendiary devices. Red phosphorus is in the material stuck on the side of matchboxes, used to strike safety matches against to light them.

By far the largest use of phosphorus compounds is for fertilisers. Ammonium phosphate is made from phosphate ores. The ores are first converted into phosphoric acids before being made into ammonium phosphate.

Phosphorus is also important in the production of steel. Phosphates are ingredients in some detergents, but are beginning to be phased out in some countries. This is because they can lead to high phosphate levels in natural water supplies causing unwanted algae to grow. Phosphates are also used in the production of special glasses and fine chinaware.

Biological role

Phosphorus is essential to all living things. It forms the sugar-phosphate backbone of DNA and RNA. It is important for energy transfer in cells as part of ATP (adenosine triphosphate), and is found in many other biologically important molecules. We take in about 1 gram of phosphate a day, and store about 750 grams in our bodies, since our bones and teeth are mainly calcium phosphate. Over-use of phosphates from fertilisers and detergents can cause them to pollute rivers and lakes causing algae to grow rapidly. The algae block out light stopping further photosynthesis. Oxygen dissolved in the water soon gets used up and the lake dies.

Natural abundance

Phosphorus is not found uncombined in nature, but is widely found in compounds in minerals. An important source is phosphate rock, which contains the apatite minerals and is found in large quantities in the USA and elsewhere. There are fears that ‘peak phosphorus’ will occur around 2050, after which our sources will dwindle.

White phosphorus is manufactured industrially by heating phosphate rock in the presence of carbon and silica in a furnace. This produces phosphorus as a vapour, which is then collected under water. Red phosphorus is made by gently heating white phosphorus to about 250°C in the absence of air.

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History

History

Elements and Periodic Table History

Phosphorus was first made by Hennig Brandt at Hamburg in 1669 when he evaporated urine and heated the residue until it was red hot, whereupon phosphorus vapour distilled which he collected by condensing it in water. Brandt kept his discovery secret, thinking he had discovered the Philosopher’s Stone that could turn base metals into gold. When he ran out of money, he sold phosphorus to Daniel Kraft who exhibited it around Europe including London where Robert Boyle was fascinated by it. He discovered how it was produced and investigated it systematically. (His assistant Ambrose Godfrey set up his own business making and selling phosphorus and became rich.)

When it was realised that bone was calcium phosphate, and could be used to make phosphorus, and it became more widely available. Demand from match manufacturers in the 1800s ensured a ready market.

Glossary

Atomic radius, non-bonded
Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. These values were determined using several different methods.

Covalent radius
Half of the distance between two atoms within a single covalent bond. Values are given for typical oxidation number and coordination.

Electron affinity
The energy released when an electron is added to the neutral atom and a negative ion is formed.

Electronegativity (Pauling scale)
The tendency of an atom to attract electrons towards itself, expressed on a relative scale.

First ionisation energy
The minimum energy required to remove an electron from a neutral atom in its ground state.

Atomic data

Atomic data

Atomic radius, non-bonded (Å)1.80Covalent radius (Å)1.09Electron affinity (kJ mol−1)72.037Electronegativity
(Pauling scale)2.19Ionisation energies
(kJ mol−1) 

1st

1011.812

2nd

1907.467

3rd

2914.118

4th

4963.582

5th

6273.969

6th

21267.395

7th

25430.64

8th

29871.9

Glossary

Bond enthalpy (kJ mol−1)
A measure of how much energy is needed to break all of the bonds of the same type in one mole of gaseous molecules.

Bond enthalpies

Bond enthalpies

Covalent bondEnthalpy (kJ mol−1)Found inP–P201P4P≡P488.3P2H–P322PH3

Glossary

Common oxidation states

The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Uncombined elements have an oxidation state of 0. The sum of the oxidation states within a compound or ion must equal the overall charge.

Isotopes

Atoms of the same element with different numbers of neutrons.

Key for isotopes

Oxidation states and isotopes

Oxidation states and isotopes

Common oxidation states5, 3, -3IsotopesIsotopeAtomic massNatural abundance (%)Half lifeMode of decay 31P30.974100- - 

Glossary

Data for this section been provided by the British Geological Survey.

Relative supply risk

An integrated supply risk index from 1 (very low risk) to 10 (very high risk). This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores.

Crustal abundance (ppm)

The number of atoms of the element per 1 million atoms of the Earth’s crust.

Recycling rate

The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply.

Substitutability

The availability of suitable substitutes for a given commodity.
High = substitution not possible or very difficult.
Medium = substitution is possible but there may be an economic and/or performance impact
Low = substitution is possible with little or no economic and/or performance impact

Production concentration

The percentage of an element produced in the top producing country. The higher the value, the larger risk there is to supply.

Reserve distribution

The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply.

Political stability of top producer

A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.

Political stability of top reserve holder

A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.

Supply risk

Supply risk

Relative supply risk5Crustal abundance (ppm)567Recycling rate (%)UnknownSubstitutabilityUnknownProduction concentration (%)38.5Reserve distribution (%)44.7Top 3 producers

• 1) China
• 2) Mexico
• 3) Morocco

• 1) Morocco
• 2) China
• 3) USA

Glossary

Specific heat capacity (J kg−1 K−1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.

Young's modulus

A measure of the stiffness of a substance. It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.

Shear modulus

A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.

Bulk modulus

A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.

Vapour pressure

A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

Pressure and temperature data – advanced

Specific heat capacity
(J kg−1 K−1)769Young's modulus (GPa)UnknownShear modulus (GPa)UnknownBulk modulus (GPa)10.9 (red); 4.9 (white)Vapour pressure Temperature (K)40060080010001200140016001800200022002400Pressure (Pa)-----------

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Podcasts

Podcasts

Listen to Phosphorus Podcast

Transcript :

Chemistry in its element: phosphorus

(Promo)

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

(End promo)

Chris Smith

Hello - this week fertilisers, fire bombs, phossy jaw and food additives. What's the connection? Here's Nina Notman.

Nina Notman

Phosphorus is a non-metal that sits just below nitrogen in group 15 of the periodic table. This element exists in several forms, of which white and red are the best known.

White phosphorus is definitely the more exciting of the two. As it glows in the dark, is dangerously flammable in the air above 30 degrees, and is a deadly poison. Red phosphorus however has none of these fascinating properties.

So where did it all begin? Phosphorus was first made by Hennig Brandt in Hamburg in Germany in 1669. When he evaporated urine and heated the residue until it was red hot. Glowing phosphorus vapour came off and he condensed it under water. And for more than 100 years most phosphorus was made this way. This was until people realised that bone was a great source of phosphorus. Bone can be dissolved in sulfuric acid to form phosphoric acid, which is then heated with charcoal to form white phosphorus.

White phosphorus has found a range of rather nasty applications in warfare. It was used in the 20th century in tracer bullets, fire bombs, and smoke grenades. The scattering of phosphorus fire bombs over cities in World War II caused widespread death and destruction. In July 1943, Hamburg was subject to several air raids in which 25,000 phosphorus bombs were dropped over vast areas of the city. This is rather ironically considering where phosphorus was first made.

Another group of warfare agents based on phosphorus are nerve gases such as sarin. Sarin is a fluorinated phosphonate that was used by Iraq against Iran in the early to mid-1980s. And was also released in a Tokyo subway in 1995, killing 12 people and harming nearly a thousand others.

White phosphorus has also found a wide range of other uses. One of these was in phosphorus matches that were first sold in Stockton-on-Tees in the UK in 1827. This created a whole new industry of cheap lights - but at a terrible cost. Breathing in phosphorus vapour led to the industrial disease phossy jaw, which slowly ate away the jaw bone. This condition particularly afflicted the girls who made phosphorus matches. So these were eventually banned in the early 1900s and were replaced by modern matches which use either phosphorus sulfide or red phosphorus.

As well as in matches, today phosphorus has found other uses in lighting. Magnesium phosphide is the basis of self-igniting warning flares used at sea. When it reacts with water it forms the spontaneously flammable gas, diphosphine which triggers the lighting of the flare.

Super pure phosphorus is also used to make light emitting diodes. These LEDs contain metal phosphides such as those of gallium and indium.

In the natural world the elemental form of phosphorus is never encountered. It is only seen as phosphate, and phosphate is essential to life for numerous reasons. It is part of DNA, and also constitutes a huge proportion of teeth enamel and bones in the form of calcium phosphate. Organophosphates are also important, such as the energy molecule ATP and the phospholipids of cell membranes.

A normal diet provides our bodies with the phosphate it needs. With tuna, chicken, eggs and cheese having lots. And even cola provide us with some, in the form of phosphoric acid.

Today most of our phosphorus comes from phosphate rock that is mined around the world, and then converted to phosphoric acid. Fifty million tonnes are made every year and it has multiple uses. It is used to make fertilisers, animal feeds, rust removers, corrosion preventers, and even dishwasher tablets.

Some phosphate rock is also heated with coke and sand in an electric furnace to form white phosphorus which is then converted to phosphorus trichloride and phosphorous acid. And it is from these that flame retardants, insecticides, and weed-killers are made. A little is also turned into phosphorus sulfides which are used as oil additives to reduce engine wear.

Phosphate is also environmentally important. It naturally moves from soil, to rivers, to oceans, to bottom sediment. Here it accumulates until it is moved by geological uplift to dry land so the circle can start again. During its journey, phosphate passes through many plants, microbes, and animals of various eco-systems.

Too much phosphate however can be damaging to natural waters because it encourages unwanted species like algae to flourish. These then crowd out other forms of desired life. There is now a legal requirement to remove phosphate from wastewaters in many parts of the world, and in the future this could be recycled as a sustainable resource so that one day the phosphate we flush down sinks and toilets might reappear in our homes in other guises such as in dishwasher tablets and maybe even in our food and colas.

Chris Smith

Nina Notman with the tale of Phosphorus, the element extracted from the golden stream, otherwise known as urine. Next time Andrea Sella will be joining us with the explosive story of element number 53.

Andrea Sella

In 1811 a young French chemist, Bernard Courtois, working in Paris stumbled across a new element. His family's firm produced the saltpetre needed to make gunpowder for Napoleon's wars. They used wood ash in their process and wartime shortages of wood forced them instead to burn seaweed. Adding concentrated sulphuric acid to the ash, Courtois, obtained an astonishing purple vapour that crystallized onto the sides of the container. Astonished by this discovery he bottled up the greyish crystals and sent them to one of the foremost chemists of his day Joseph Guy-Lussac who confirmed that this was a new element and named it iode - iodine - after the Greek word for purple.

Chris Smith

And you can hear more about how Iodine exploded onto the world's stage on next week's Chemistry in its Element, I hope you can join us. I'm Chris Smith, thank you for listening and goodbye.

(Promo)

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements.

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How many protons are in phosphorus?

How many protons and electrons are in phosphorus?

Does phosphorus have 15 protons and 16 electrons?

How many electrons does phosphorus contain?