Lesson 1.3 - Elements

In this lesson:

• What are elements?

• Element symbols

• Common symbols

• Periodic table

• Common elements

• Group 1 elements

• Group 7 elements

Elements

An element is a type of atom.

It is determined by the number of protons the atom has.

Elements are represented by different symbols.

Element symbols

Each elements has a unique symbol.

These symbols identify an element in a chemical reaction.

Some elements have 1-letter symbols (e.g. O for oxygen). Some have 2-letter symbols (e.g. He for helium).

Common element symbols

As of this document, there are 118 elements.

Below are some common ones:

Symbol	Element Name
O	Oxygen
N	Nitrogen
Si	Silicon
Na	Sodium
Mg	Magnesium
Og	Oganesson
H	Hydrogen
He	Helium
Li	Lithium

Periodic table

The elements can all be found on the periodic table.

It shows the electron configuration, the relative atomic mass, the state of matter, the number of protons, etc.

It's very useful :)

Common elements

The first 20 elements are listed below:

• Hydrogen (H)

• Helium (He)

• Lithium (Li)

• Beryllium (Be)

• Boron (B)

• Carbon (C)

• Nitrogen (N)

• Oxygen (O)

• Fluorine (F)

• Neon (Ne)

• Sodium (Na)

• Magnesium (Mg)

• Aluminium (Al)

• Silicon (Si)

• Phosphorus (P)

• Sulphur (S)

• Chlorine (Cl)

• Argon (Ar)

• Potassium (K)

• Calcium (Ca)

Group 1

Group 1 elements include:

Period	Symbol	Element	Atomic number	Atomic mass
2	Li	Lithium	3	7
3	Na	Sodium	11	23
4	K	Potassium	19	39
5	Rb	Rubidium	27	85.5
6	Cs	Caesium	55	133
7	Fr	Francium	87	223

These elements are called the alkali metals.

Group 7

Period	Symbol	Element	Atomic number	Atomic mass
2	F	Fluorine	9	19
3	Cl	Chlorine	17	35.5
4	Br	Bromine	35	80
5	I	Iodine	53	127
6	At	Astatine	85	210
7	Ts	Tennessine	117	294

These are the halogens, and are non-metals.

Contents

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