What is the Periodic Table of Elements?
The Periodic Table of Elements
● Publisher: Dmitri Mendeleev. Date: 1869. Contained: 63 known elements.
● First discovery of separate gas elements: 1766 by Henry Cavendish (air).
● Allows scientists (and others) to predict relationships between elements and predict properties of new ones.
● The term “atom” is a general term. Everything is made of atoms.
● The term “element” describes atoms with specific qualities.
● Elements are the building blocks of all matter.
● Lists the CHEMICAL SYMBOL, ATOMIC NUMBER, and the ATOMIC MASS of each element.
● 118 elements but only the first 18 make up most of the matter in the known universe.
These 18 elements’ electrons fit comfortably into THREE ORBITALS.
The first 94 elements occur naturally. The other 24 occur when formed in a laboratory.
Almost 75% of all ELEMENTS are classified as METALS.
ELECTRON CONFIGURATION: The arrangement of electrons in the ORBITALS of an atom, molecule or crystal.
Electrons are arranged in SHELLS at different distances around the nucleus.
Shell 1: holds a maximum of 2 electrons
Shell 2: holds a maximum of 8 electrons
Shell 3: holds a maximum of 18 electrons
Shell 4: holds a maximum of 32 electrons
Moving across each ROW of the PERIODIC TABLE the PROTON number increases by ONE for each element. The number of ELECTRONS also increases by ONE for each element.
118 Elements but Only the First 18 Make up Most of the Matter in the Known Universe
● Metals: conduct heat or electricity.
● Non-Metals: DO NOT conduct heat or electricity.
● Semi-Metals: Have the properties of metals and non-metals.
● Nobel Gases: Do not combine with other elements.
Some Helpful Facts
● The hardest natural substance on Earth is DIAMOND. Strangely it is rather brittle and if hit (with a hammer) will usually shatter.
● A non-metal which conducts electricity is GRAPHITE.
● The only metal that is liquid at room temperature is MERCURY.
● The lightest Chemical Element is Hydrogen (H). The heaviest is Hassium (Hs).
● Hydrogen sits in Group 1 but is not an Alkali Metal.
● Cobalt, Iron and Nickel are MAGNETIC. Apart from STEEL (which is a mixture that is mainly IRON) the other metal elements are NOT magnetic.
● Three metals (iron, cobalt and nickel) are MAGNETIC. Steel is a mixture of elements but it is mostly iron, so it is also magnetic. The other metal elements are not magnetic.
● ATOMS with atomic numbers higher than 92 do not exist naturally. They are created by bombarding ELEMENTS with other ELEMENTS.
● ELEMENTS are arranged by their number of PROTONS (atomic number).
● ALKALI METALS can explode if exposed to water.
Understanding The Organisation of the Periodic Table
● Each element is placed in a specific location depending on its ATOMIC STRUCTURE.
● 9 ROWS (PERIODS) read left to right (based on their ATOMIC NUMBER i.e. the number of PROTONS in their NUCLEUS).
● 18 COLUMNS (GROUPS) read top to bottom. Sometimes notated as 1-7 and 0 (first two columns on the left and last six columns on the right)
● Each row and column has specific characteristics.
● Elements in different rows share different characteristics. Elements in different columns share specific similarities.
● All elements in a PERIOD have the same number of ATOMIC ORBITALS. As you go down the table each row adds an ORBITAL (from one to seven).
● Each vertical column is called a GROUP.
● The elements in each GROUP have the same number of ELECTRONS in the OUTER ORBITAL (also called VALENCE ELECTRONS).
● All elements in GROUP ONE (first column) has one electron in its OUTER SHELL. As you go along the columns add one electron.
● As the ATOMIC NUMBERS increase the elements become rarer in nature and also usefulness.
● The two rows under the main PERIODIC Table are the LANTHANIDE and ACTINIDE series.
● LANTHANIDE (15 elements) can be found naturally on earth.
● ACTINIDE (15 elements) are radioactive and are not all found in nature.
The main ones to memorise;
● Actinide, Alkali, Lanthanide (also sometimes called Rare EarthMetals), Rare and Transition (Metals).
● Alkaline and Rare (Earth Metals).
Identify a metal using;
● CONDUCTION: Metals are good at conducting electricity.
● REACTIVITY: Metals are very reactive (form compounds with other elements).
● ALLOYS: Metals are easily mixed to form ALLOYS.
● ALL Actinides are RADIOACTIVE.
● Some are synthetically produced while others are found in nature.
● Uranium and Thorium are naturally occurring.
● Plutonium is synthetically produced.
Alkali Earth Metals
● Alkali EARTH Metals are in group 2.
● They are reactive but NOT as reactive as Alkali Metals.
● All Alkali Earth Metals occur in nature.
● Alkali Metals are in group 1.
● They are VERY REACTIVE and DO NOT occur freely in nature.
● They have only ONE electron in their outer shell.
● Good conductors of heat and electricity.
● Basic (Base) Metals are on a step-line in groups 3-6 (13-16).
● They are commonly found and are not considered valuable (inexpensive).
● They oxidise and corrode very easily.
● Base Metals refers to industrial NON-FERROUS metals (excluding precious metals).
● Halogens are in group 7.
● Halogens is from the Greek word which means “SALT-MAKERS”.
● Halogen elements have seven VALENCE ELECTRONS.
● Also known as RARE-EARTH metals.
● Some of these elements are used in glass production, lasers, or superconductors.
● Using ion-exchange, separation of an individual element is easier and more precise.
● Sometimes know as semi-metals.
● Placed along step-line between metals and non-metals.
● Have the same properties as both metals and non-metals.
● Some are semi-conductors (used in computers).
NOBLE GASES (non-metals)
● Once called INERT GASES (non-reactivity). But discoveries since then revealed there were other gases that were inert but not NOBLE GASES.
● All NOBLE GASES are located in the far right column of the Periodic Table (GROUP ZERO).
● Noble Gases are in group 18.
● They are the MOST STABLE due to the number of VALENCE ELECTRONS their outer shell can hold.
● They rarely react with other elements since they are already STABLE.
● They all conduct electricity.
● They are odourless and colourless.
● Non-metals are in group 1 (H) and groups 4-6 (14-16).
● Non-metals are very brittle.
● Non-metals are poor conductors of heat and electricity.
● They do not reflect light.
● Some non-metals are liquids.
● Found running along the centre of the Periodic Table between groups 2 and 3 (the D block).
● Usually hard and dense.
● Less reactive than Alkali Metals.
A Final Thought
Trying to put even the basics of the Periodic Table into easy to understand (by me) bite-sizes tested my rudimentary writing skills to the limit.
If you are studying and learning all about the Periodic Table then good on you, and I wish you well.
If you see any mistakes please let me know.