Electricity is vital to our civilization. So what is electricity and how does it work? To explain electricity we need to zoom passedthe molecular and into the atomic level. Atoms are the smallest things we can kindof see, but not with the naked eye: Only with a scanning tunnelling microscope can we geta glimpse of somewhat fuzzy spheres. To really understand electricity, we mustgo even further and look inside an atom. This is where it gets complicated, becausethe inside of an atom cannot be seen, at least not at the time of writing. So, we’ll use this representation of theinside of an atom. This is called the Bohr-model, keep in mindthat it is not to scale, and only two-dimensional. This model is also known as the planetarymodel, modelling the parts of an atom as planets orbiting a sun – or moons around a planet. While actually, these orbiting moons are notat any one place at any one time at all, but exist more as regions, or clouds, around thecore. However inaccurate the Bohr-model might be,it will do for our explanation of electricity. Atoms consist of protons and neutrons, theseform the nucleus of the atom. Orbiting the nucleus are the electrons. It’s these electrons that are responsiblefor electricity, hence the name.
Think of these orbits more as shells, surroundingthe nucleus. What type of atom – which element – itis, is defined by the number of protons in the nucleus, at the centre. Atoms of one element all have the same numberof protons, but can have different numbers of neutrons and electrons. It’s this variable number of electrons,that is important to our understanding. Electrons – which are far lighter than theprotons in the nucleus – can relatively easily move. And this is important, because the movementof electrons is what forms an electric current. The atom’s protons account for the positivecharge of the nucleus, and the electrons for the negative charge. In a stable, resting, or rather, neutral electricalcondition, these charges balance each other out within the atom. This gives the atom a net electric chargeof zero, for each positive proton you will find one negative electron. In this state the atom is at its lowest possibleenergy level, which we call the ground state of the atom. However, we can change the atom’s charge,or energy level, by causing it to gain or lose electrons. When the atom has fewer electrons than protons,it becomes positively charged. But when the atom has more electrons thanprotons, the net charge swings back the other way, and it becomes negatively charged. More electrons than protons mean the atomis negatively charged, fewer electrons than protons mean it is positively charged. Losing or gaining electrons changes the atom’selectric charge. The remainder of this video we will colourcode the atoms, as follows: A positive charge – or absence of electrons– is represented with red. A negative charge – a surplus of electrons– is represented with blue. A neutral charge – or a balance betweenelectrons and protons – is represented by a blend of red and blue: Purple.
So, when in a ground state or uncharged, itlooks like this – and it’s called an atom. When charged, negatively or positively, itlooks like these. Instead of atoms, when there is a charge,they are called a negative or positive ion. Each shell of an atom can hold a maximum numberof electrons. The inner shell can hold 2 electrons, thesecond can hold 8, the third 18, and there are elements with all seven known shells. Shells are populated with electrons from theinside out. Meaning that added electrons always go forthe inner-most shell possible with a spot left. The number of electrons on the outermost shelldetermines the reactivity of the atom. This shell is called the valence shell, andits electrons are called valence electrons. When the outermost shell is full, the atomis generally stable and least reactive. You may be familiar with the term and effectsof static electricity. When you, for instance, shuffle your feetover a nice, soft carpet… …you build up a positive charge, becausenegatively charged electrons are being lost to the carpet. Carpets are often made from a material withthe properties of an insulator.
