Alkali Metals

Lithium Sodium Potassium Rubidium Caesium Francium

Li

Na

K

Rb

Cs

Fr

Lithium is used to make batteries. If you have not heard of Lithium ion batteries you must live in the “Stone Age”.

Sodium is required by our nerves and muscles. It is present in almost everything which we eat. Table salt is Sodium Chloride.

Potassium is also required by nerves and muscles. It is also present in almost everything we eat.

Cells can pump sodium ions, potassium ions and chloride ions across their membranes. This is called the “sodium pump”, it requires energy from ATP. When nerve cells and muscle cells pump these ions an and out of their cells they generate a membrane potential. When a nerve cell stops pumping ions for a fraction of a second, a nerve impulse travels along the nerve. A similar thing happens when a muscle contracts.

Caveat

Electrons have a very tiny mass: they don’t have “Zero Mass” as it says in the animation. However, you don’t need to take account of their mass when you are calculating molecular weights: for your purposes, the atomic mass is calculated by adding the number of neutrons to the number of protons.

Since electrons do actually have some mass, they cannot travel at the speed of light. They would need an infinite amount of energy to travel this fast. However, they do buzz around the atomic nucleus at very fast speeds.

When an atom is excited, ie. it has too much energy, electrons can escape from their normal orbits into higher energy orbits or escape the atom completely; this would leave the atom in an ionised state.

The animation shows electron pairs: since electrons have negative charges, they repel each other so they would normally be at opposite ends of their orbit.

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