Group 0 - The Noble Gases

What are the noble gases?

The noble gases are helium, neon, argon, krypton, xenon and radon (radioactive).


Properties of the noble gases

• They are all non metals
• They were discovered after Mendeleev had invented the periodic table
• Colourless gases
• Exists as monatomic gases, e.g. Ar, Ne, He etc. 
• Very unreactive
• Also called Group VIII
• Very steady electron structures that are difficult to change
• Other elements try to get these electron configurations by under going chemical reactions
• Their outer electron shells are full

Compounds of helium, neon and argon have never been found, but recently, compounds of xenon and krypton with fluorine and oxygen have been found, e.g. XeF.

Uses of argon, neon and helium

Neon is used in lasers and neon lights.

Argon gas is the gas used in lightbulbs that stops the tungsten filament reacting with air.

Helium is used in balloons and medical procedures, e.g. MRI machines.

You can separate helium from natural gas by liquefying the other elements.

You can also obtain the other noble gases by the fractional distillation of liquid air.

Acids and Alkalis - Basic

What are acids and alkalis?

Acids are all: sour, corrosive and soluble in water
All alkalis are the chemical opposite of acids, have a soapy feel and can remove the sharp taste from acids.

Examples of acids:

• Vinegar
• Orange juice
• Lemons and limes

Examples of alkalis:

• Bleach
• Toothpaste
• Washing powder
• Milk of magnesia

Indicators

Indicators are used to test if a substance is acidic, they change colour when added to acids or alkalis. Many indicators are actually dyes that have been extracted from a natural source, e.g litmus. The table below helpfully shows some common indicators and the colours that they turn when you add them to acids or alkalis.

Universal Indicator

The universal indicator is used to find out how acidic or alkaline a substance is.

It's a mix of several different indicators and it can be used as a paper or as a liquid, it turns a different colour depending on what acid or alkali is added to it. You then match up the colour of the universal indicator with something called the pH scale. 

The pH scale.
Image courtesy of https://www.chinesemedicineliving.com

Each colour on the pH scale corresponds to a number, and the number tells you the pH level of the substance you're testing. For example, the pH of pure water is 7.

What the pH level tells you about a substance

• pH of less than 7 - acid
• pH of 7 - neutral
• pH of more than 7 - alkaline

pH meter
Image courtesy of http://www.conrad-electronic.co.uk

Another method of measuring the pH of a substance is to use a pH meter.

When you place the electrode into the solution, the electronic display shows the pH level.