Everything in the world is made from about 100 elements and these are found in the Periodic
Table
Each element has a name and a symbol unique to it
Name of Element
Symbol of Element
Hydrogen
H
Helium
He
Potassium
K
Chlorine
Cl
The first letter is always a capital letter. If there is a second letter then it is lower case.
Classify elements in different ways:
Classification Type
Examples
Naturally occurring/made All elements with atomic number above 92 are made by
by scientists
scientists and are not found naturally on Earth
Solid/Liquid/Gas
The majority of elements are solid. There are 11 gases (Mainly
found on the right of the Periodic Table). Bromine and Mercury
are the only liquids
Metal/Non-Metal
Metals are found on the left of the steps
Non-Metals are found on the right of the steps
Elements are classified by arranging the in the Periodic Table
- a group is a column of elements in the Periodic Table
- a period is a horizontal row in the in the Periodic Table
Elements in the same group of the Periodic Table show similar chemical properties
- Lithium, sodium and potassium all react quickly with water and are all found in group 1
- Noble gases are a family of very unreactive elements and are found in Group 0
There are 5 families of elements to learn
Name
Group
Examples
Alkali Metals
Group 1
Lithium, Sodium, Potassium
Alkaline Earth Metals
Group 2
Magnesium, Calcium
Transition Metals
Block between Groups 2 and 3 Gold, Iron, Copper
Halogens
Group 7
Fluorine, Chlorine, Bromine
Noble Gases
Group 8/0
Helium, Neon, Argon
Every element is made up of very small particles called atoms. Atoms have the following
structure:
Green
Amber
Learning Statement
Red
Smithycroft Secondary
Chemistry
Unit 1: Section 2 – Atomic Structure and
the Periodic Table
Atoms are made up from 3 different particles:
Particle
Location
Charge
Mass
Proton
Nucleus
+1
1 a.m.u
Neutron
Nucleus
Neutral
1 a.m.u
Electron
Outside the Nucleus
-1
Almost 0
Atoms are neutral because;
- The positive charge of the nucleus is equal to the sum of the negative charges of the
electrons
- They have the same number of protons and electrons
Electrons are arranged in electron shells which are sometimes called energy levels
1st Energy Level Holds
2nd Energy Level Holds
3rd Energy Level Holds
2 Electrons
8 Electrons
8 Electrons
Electrons arrangements of the 1st 20 elements are found on page 1 of the data booklet
Elements with the same group have the same number of outer electrons e.g. Group 1 Alkali
Metals
Lithium
Sodium
Potassium
2,1
2,8,1
2,8,8,1
Elements with the same number of electrons in their outer shell have the same chemical
properties
Each element on the Periodic Table has its own atomic number
- The atomic number is the number of protons
The mass number of an atom is equal to the number of protons plus neutrons
The number of protons, neutrons and electrons of neutral atoms can be calculated by the
following:
Isotopes are atoms of the same element which have:
- the same atomic number but a different mass numbers
- the same number of protons but a different number of neutrons
Most elements have more than on isotope
Relative atomic mass is the average atomic mass of all the isotopes of an element
- RAM is rarely a whole number because it an average
e.g. the RAM of chlorine is 35.5
- The two chlorine isotopes are 35Cl and 37Cl
As RAM is closer to 35 than 37 there must be more 35Cl atoms in sample than 37Cl atoms
Compounds are formed when elements react together.
- 2 or more different elements chemically joined together by bonds
1
A mixture occurs when two or more substances come together without reacting
Compounds can be named using the following rules:
Name Ending
Meaning
Contains the two named elements in the compound name
-ide
-ate
-ite
Contains the two named elements in the compound plus oxygen
Contains the two named elements in the compound plus oxygen
Examples of the elements found in compounds:
Compound
Elements in Compound
Sodium Chloride
Sodium + Chlorine
Copper Sulphate
Copper + Sulphur + Oxygen
Potassium Nitrite
Potassium + Nitrogen + Oxygen
Atoms can be held together by bonds to form molecules
- atoms share electrons to achieve a stable electron arrangement
A covalent bond is the attraction of the shared pair of the electrons for both nuclei in nonmetal elements
A molecule is a group of atoms held together by covalent bonds
a diatomic molecule is made up of two atoms:
2