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Table of Contents Atomic Symbols
Checkpoint 1
Chemical Formula
Covalent 1
Covalent 2
Ionic 1
Ionic 2
Checkpoint 2
Summary



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Learning Zone - Chemical Symbols and Formula

covalent 2 Ionic Compounds 1 ionic compounds 2

An ionic compound is formed via ionic bonds. The chemical formula of an ionic compound can be determined by summing up the charges on the ions (charged atoms) that made up the ionic compound.

The total charges on the constituent ions are cancelled out (net zero) to give a neutral ionic compound.

Table below lists some of the common ions.

Ions

Symbols

Symbols

Symbols

Sodium

Na+

Chloride

Cl-

Potassium

K+

Bromide

Br-

Calcium

Ca2+

Iodide

I-

Aluminium

Al3+

Oxide

O2-

Iron(II)

Fe2+

Hydroxide

OH-

Iron(III)

Fe3+

Sulphate

SO42-

Ammonium

NH42+

Carbonate

CO32-

Charged atoms are called ions. The superscripts show the charge values. For example, sodium ion (Na+) has a charge of positive one (written as + not 1+). The magnesium ion (Mg2+) has two positive charge (written as 2+). Similar notation works for the negatively charged ions.

Some ions can have more than one charge values. This is especially true for the transition metals. For instance, iron can form two different ions, iron(II) and iron(III), and the Roman numerals refer to the charge values.

Some ions are made up of a group of atoms. It comes as a single entity and form ionic bonds with other ions. For instance, the carbonate anion, with the chemical symbol CO32-.

For a neutral atom, the charge is zero and no superscript number is needed. For example, neutral sodium atom, Na.

Also, these superscript charge values are usually shown in a chemical formula only when the charges are not balanced.

Covalent 2 ionic compounds 2

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