Atoms and Electricity

The atom is considered the basic building block of all materials.

Structure of Atoms

Atoms are made of a small, compact, central nucleus surrounded by electrons. Inside the nucleus are positively charged protons and uncharged neutrons.* Negatively charged electrons orbit the nucleus.

Neutral atoms have equal numbers of protons and electrons. Thus, the positive and negative charges cancel each other, and these atoms have no overall charge.

*All atoms have protons and neutrons except for hydrogen in its most common form, which has a proton but no neutron.

The element box of carbon from the periodic table of elements shows the atomic number (the number of protons) above the symbol, C, for carbon, and the mass of a carbon atom.	This model of a carbon atom shows the six protons (protons are represented as P+) and six neutrons (N) in the nucleus. Six electrons (e-) orbit in clouds surrounding the nucleus.

Atoms, Moving Electrons, and Charges

Atoms with incomplete outer orbits will readily lose electrons or will readily accept additional electrons. Electrons in the outer orbits are called valence electrons. The outer orbit is called the valence shell.

The periodic table of elements arranges atoms in columns or families of elements by the number of valence electrons. How ready an atom is to lose or gain an electron determines its reactivity. The furthest right column on the periodic table contains elements (the noble gases) whose atoms have complete valence shells. They don't accept or give up electrons. These elements are considered inert, or unreactive.

The Periodic Table of Elements

Note that there are many more metal elements (white) on the left side of the stairstep divider than nonmetal elements (red) on the right side of the divider.

Valence electrons in a metal atom's outermost orbits are able to gain energy and escape to be free electrons. They can also join other atoms to complete their valence shells. Negatively charged electrons are attracted to positive charges. The closer to a nucleus, the stronger the attraction. When electrons are lost by an atom (usually to empty the orbit of valence electrons), an atom becomes a positively charged ion. This is because the atom now has more positive than negative charges.

The element box of sodium shows the atomic number; the symbol, Na; and the average mass of a sodium atom.	These models show a neutral sodium atom (a metal) and a positively charged sodium ion after sodium loses the one electron in its outer orbital.

If an atom accepts one or more extra electrons (usually to fill the valence shell), it becomes a negatively charged ion. This is because the atom now has more negative than positive charges.

The element box of chlorine shows the atomic number; the symbol, Cl; and the average mass of a chlorine atom.	These models show a neutral chlorine atom (a nonmetal) and a negatively charged chloride ion after chlorine gains an electron to complete its outer orbital.

Electrons move along conducting materials (like copper wire) from the negative side to the positive side of the dry cell. The difference between the electric potentials of the dry cell's two metal terminals is the voltage of the battery.

This difference between the metals along with the conductive material between them allows electricity (the movement of electrons), or electric charge, to flow. The greater the potential difference between the two terminal materials in a battery or dry cell, the greater the voltage of the battery.

You'll have an opportunity to work with voltage, the potential difference that causes current to flow, in the computer and hands-on activities.