Elements Compounds
An Element is a pure substance that cannot be broken down into simpler substances by chemical or physical methods. An element is composed of only atoms of the same type of atom i.e. the same number of protons in their nuclei.
A Compound is a substance composed of two or more different elements chemically combined in a definite proportion. The properties of a compound are different to those of the elements it is made of. The chemical bonding of two or more elements in the formation of a compound produces a new substance with new properties.
Only 92 elements occur naturally– number 1 is hydrogen, number 92 is uranium. About 24 ‘artificial’ elements have been produced in laboratories. The Elements are arranged in the Periodic Table, on page 44 of the Mathematics Tables. The elements are represented by symbols. The 1st 2 elements Hydrogen & Helium make up the most of the atoms in the universe. There are over 10 million different known pure substances.
Only 116 are elements; all the others are compounds. Like 26 letters in the Alphabet but millions of words!!!
Non-metallic Elements: Names, Symbols Note location of the non-metals in the Periodic Table (metal steps).
* Can show metallic properties
Property
State
MP / BP
Density
Chrctrstc Test
Hydrogen (H)
Gas
-259°C / -253°C
0.00089 g/cc
Burns with a ‘pop’
Oxygen (O)
Gas
-218°C / -183°C
0.0014 g/cc
Relights a glowing splint
Water (H2O)
Liquid
0°C / 100°C
1 g/cc
blue cobalt chloride pink
The elements of a compound always occur in fixed ratio of mass. In water hydrogen is always one ninth of the total mass and oxygen is always eight ninths. The mass ratio of hydrogen to oxygen is always 1:8 in water.
About 80% of the elements are Metals. In the Periodic Table the metals are to the left of a zig-zag line formed by B, Si, As, Te and At.
Some Metallic Elements: Names, Symbols, Uses
A Compound is a substance composed of two or more different elements chemically combined in a definite proportion. The properties of a compound are different to those of the elements it is made of. The chemical bonding of two or more elements in the formation of a compound produces a new substance with new properties.
The formation of a new substance with new chemical properties is known as a chemical change.
Common Compounds and their Constituent Elements
Water: H and O. Glass: Si and O. Table Salt: Na and Cl
Glucose & Fat: C, H and O. Protein: C, H, O and N Plastic: H and C