is the monatomic ion occur naturally? if not how this kind of ion existed? if wonder if the nature is the same with atom with different isotopes. thank you in advance.

Monatomic ions do occur naturally. Atoms naturally form monatomic ions during chemical reactions, when ionic compounds melt, and when electrolytes dissociate in water. For example, when NaCl (table salt) dissolves in water, it forms the monatomic ions Na+ and Cl-. Atoms form monatomic ions to achieve the most stable electron configuration.

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Course: High school chemistry > Unit 2

Lesson 3: Polyatomic ions

Polyatomic ions

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Learn what polyatomic ions are and how to write them in chemical formulas.

Some ions consist of a single atom with a net charge. They're called monatomic ions. Examples include

{Na}^{+}

O^{2 -}

, and

{Cl}^{-}

Other ions consist of a group of atoms with a net charge. Since these ions are composed of multiple atoms covalently bonded together, they are called polyatomic ions.

Let's explore some of the most common polyatomic ions and learn how to write chemical formulas for compounds containing these ions.

Examples of polyatomic ions

Some common polyatomic ions are listed below.

Name	Chemical formula
hydroxide	$OH^{-}$ ‍
acetate	$C_{2} H_{3} O_{2}^{-}$ ‍
nitrite	$NO_{2}^{-}$ ‍
nitrate	$NO_{3}^{-}$ ‍
carbonate	$CO_{3}^{2 -}$ ‍
sulfite	$SO_{3}^{2 -}$ ‍
sulfate	$SO_{4}^{2 -}$ ‍
phosphate	$PO_{4}^{3 -}$ ‍
ammonium	$NH_{4}^{+}$ ‍

Here are some more!

Name	Chemical formula
cyanide	$CN^{-}$ ‍
hydrogen carbonate (bicarbonate)	$HCO_{3}^{-}$ ‍
hypochlorite	$ClO^{-}$ ‍
chlorite	$ClO_{2}^{-}$ ‍
chlorate	$ClO_{3}^{-}$ ‍
perchlorate	$ClO_{4}^{-}$ ‍
permanganate	$MnO_{4}^{-}$ ‍
chromate	$CrO_{4}^{2 -}$ ‍
dichromate	$Cr_{2} O_{7}^{2 -}$ ‍
peroxide	$O_{2}^{2 -}$ ‍

Bonding with polyatomic ions

Like monatomic ions, polyatomic ions participate in ionic bonds with other ions (but remember, the atoms within a polyatomic ion molecule are held together by covalent bonds).

Polyatomic ions combine with other ions in a ratio that produces a neutral compound overall. Subscripts are used to indicate the number of ions needed to make that neutral compound.

If you need more than one polyatomic ion, enclose the ion in parentheses and add the subscript outside of the parentheses.

For example, magnesium

(Mg)

loses two electrons to form a

2 +

cation. When magnesium bonds with hydroxide

(OH^{-})

, two hydroxide ions are needed for every magnesium ion in order to form a neutral compound.

So, the formula for magnesium hydroxide is

Mg (OH)_{2}

Example 1

Potassium sulfate consists of potassium ions and sulfate ions bonded together. Potassium is an element in group 1 of the periodic table. Therefore, we know that potassium forms monatomic ions with charge

1 +

. Sulfate is a polyatomic ion. We can see in the table above that sulfate ions have a charge of

2 -

To produce a neutral compound, two

K^{+}

are needed for every

{SO_{4}}^{2 -}

. So, the formula for potassium sulfate is

K_{2} SO_{4}

The

K^{+}

and

{SO_{4}}^{2 -}

ions are held together by ionic bonds. The

S

and

O

atoms within each

{SO_{4}}^{2 -}

are held together by covalent bonds.

Example 2

Strontium nitrate is composed of strontium ions and nitrate ions bonded together. Strontium is an element in group 2 of the periodic table; it forms monatomic

{Sr}^{2 +}

ions. Nitrate is a polyatomic ion with formula

{NO_{3}}^{-}

To produce a neutral compound, one

{Sr}^{2 +}

is needed for every two

{NO_{3}}^{-}

. So, the formula for strontium nitrate is

Sr (NO_{3})_{2}

Note how parentheses are added around the polyatomic ion. This lets us indicate that the subscript $2$ ‍ applies to the entire nitrate unit.

Try it!

Calcium acetate crystals can be grown by soaking eggshells in vinegar.

Complete the statements.

Calcium ions have a charge of

Acetate ions have a charge of

So, the correct formula for calcium acetate is ______.

Ammonium nitrate $(NH_{4} NO_{3})$ ‍ is used in fertilizers and explosives. It's composed of two polyatomic ions, ammonium and nitrate, bonded together. A model of ammonium nitrate is shown below.

Complete the statements.

The

N

and

H

in each

NH_{4}^{+}

are held together by

The

N

and

O

in each

NO_{3}^{-}

are held together by

The

NH_{4}^{+}

and

NO_{3}^{-}

NH_{4} NO_{3}

are held together by

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carlo.navaro
Posted 24 days ago. Direct link to carlo.navaro's post “is the monatomic ion occu...”
is the monatomic ion occur naturally? if not how this kind of ion existed? if wonder if the nature is the same with atom with different isotopes. thank you in advance.
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- ³oɔiiᴎ
  Posted 22 days ago. Direct link to ³oɔiiᴎ's post “Monatomic ions do occur n...”
  Monatomic ions do occur naturally. Atoms naturally form monatomic ions during chemical reactions, when ionic compounds melt, and when electrolytes dissociate in water. For example, when NaCl (table salt) dissolves in water, it forms the monatomic ions Na+ and Cl-. Atoms form monatomic ions to achieve the most stable electron configuration.
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  (3 votes)