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Elements

• All substances are made of atoms.
• Substances containing one type of atom only are elements.
• When elements combine they make compounds.
• When atoms join together they make molecules.
• The difference between a pure substance and a mixture.
• The main ways to separate mixtures.
• Crude oil is a mixture of chemicals. They are separated by fractional distillation.
• There is a symbol for each element.
• There is a formula for each compound.
• Elements can sorted into metals and non-metals.
• The main properties of metals.
• The main properties of non-metals.
• The uses of an element depend on its properties.
• Metals can be put into an order of reactivity.
• Reactive metals displace less reactive metals.

Pure chemistry in this section.

• An element is made up of only one kind of atom.
• A compound has two or more different types of atom joined together.
• A mixture contains more than one element and/or compound but they are not all joined together.
• A molecule has two or more atoms joined together. These can be the same or different.

We can show atoms as little circles and you are often asked to look at diagrams and say if they contain elements, compounds, molecules or mixtures. 

Elements

• All matter in the universe is made up of atoms (extremely small particles). There are just over 100 different types of atom; each type is called an element. Each element contains only one type of atom.
• Each element has a name and a symbol, which you can find in a periodic table.
• Atoms consist of protons, neutrons and electrons.
• Protons and neutrons are found at the centre of the atom. This very small area is called the nucleus. The electrons are found outside the nucleus, orbiting it.
  1. A proton is a particle inside an atom's nucleus and has a 1+ charge
  2. A neutron is a particle inside an atom's nucleus (except hydrogen) and has zero charge
  3. An electron is a smaller particle than a proton and is found outside the nucleus. It has a 1- charge and it has nearly no mass at all

Compounds

Compounds are two or more different elements combined. Their atoms have been joined or bonded together. Here is a list of some compounds.

How to name a compound

• If a compound has a metal in it, write the metal's name first
• When a single non-metal is in a metal/non-metal compound write the non-metal second and change its ending to ide (see 1, 2, 4, 5, 6, 7 & 8)
• When there is a metal, a non-metal and oxygen the spelling of the non-metal changes its ending to ate (see 3, 5 & 9)
• Non-metal compounds - the second non-metal ends in ide (see 7 & 8)
• The words mono-, di- and tri- indicate the numbers 1, 2 and 3 of atoms of an element in the compound (e.g. Carbon dioxide has one carbon atom and two oxygen atoms).

All the elements are listed in the periodic table. They are arranged in order of increasing atomic number, which is the number of protons in the atom. Columns of elements, called groups, have similar properties. Rows of elements, called periods, have gradually changing properties.

A chemist called Mendelev developed the periodic table. He made a number of important contributions:

• He left spaces for undiscovered elements and so elements of similar chemistry were placed underneath each other. This gave the modern groups of elements.
• He changed the order of the elements so the elements with similar chemistry would be in the same group.

Reactivity series of metals

Some metals  in the reactivity series will react with water. The metals below these - like copper, silver and gold - do not react with water.

Lithium, sodium, and potassium all react well (fast, vigorously) with cold water. These metals react and dissolve, producing an alkaline solution. This is a metal hydroxide solution. This turns Universal Indicator purple. While reacting, hydrogen (which is a flammable gas) is given off. You can hear it being made by the fizzing noise.

lithium + water = lithium hydroxide + hydrogen

potassium + water = potassium hydroxide + hydrogen

sodium + water = sodium hydroxide + hydrogen

• Metals that wont react with water often react with dilute acids.
• The reaction involves:

1. The metal dissolving
2. Fizzing as hydrogen gas is being formed.
3. The test tube gets warm because the reaction produces thermal energy - i.e. it is exothermic.

• The general word equation is:

          acid + metal = hydrogen gas + a salt

• A salt is a compound made from an acid when a metal has replaced the hydrogen. The table below gives you the names of the salts formed when using each acid.

Displacement reactions

A displacement reaction happens between a reactive metal and a solution of a less reactive metal compound. The more reactive metal will displace the less reactive metal from its compound in solution.

What do you often observe (see, hear, feel) in this type of reaction?

1. The more reactive metal will dissolve.
2. The less reactive metal will appear at the bottom of the tube or plate on the more reactive metal.
3. The solution may change colour.
4. The reactions are exothermic, so the tube gets warm.

This is a list of metals in order of their chemical reactivity. The most reactive is at the top and the least is at the bottom.

 

Element	Symbol
Potassium	K	Most reactive
Sodium	Na
Calcium	Ca
Magnesium	Mg
Zinc	Zn
Iron	Fe
Lead	Pb
Copper	Cu
Silver	Ag
Gold	Au	Least reactive

Some sites to help you:-

The Internet offers a range of bits and pieces to cull for use in this section. You will find element hangman, flashcards to match element symbols to names at http://www.jlab.org/services/pced/indexpages/students.html. For revision, customise the element flashcards at http://www.quia.com/custom/786main.html. For more hangman games on science vocabulary, play at http://www.jlab.org/services/pced/vocabhangman/index.html

also check out these sites for extra information

http://learn.co.uk/default.asp?WCI=Unit&WCU=3432

www.chemsoc.org/viselements/pages/data

http://www.Colorado.EDU/physics/2000/index.pl

• Carry out test to find the properties of elements and compounds.
• Decide form the chemical name whether a substance is an element or a compound.
• Name at least 4 elements.
• Name at least 4 compounds.
• Understand box diagrams of atom and molecules.
• Separate some pure substances from mixtures.
• §Write the symbols for at least 5 elements.
• Carry out test to find the differences between metals and non-metals.
• Name at least 5 metals.
• Name at least 5 non-metals.
• Name at least one reactive metal.
• Name one at least unreactive metal.
• Plan an investigation to produce an order of reactivity for metals.
• Carry out displacement reactions.
• Predict whether a displacement reaction will take place.