Atoms & the Periodic Table (old version)

This paragraph introduces the fundamental concept of atoms, which are the smallest units of matter that constitute the universe. It explains the basic structure of an atom, highlighting the nucleus containing protons and neutrons, and the electrons orbiting in an electron cloud. The paragraph also distinguishes between an atom and an element, using aluminum foil as an example to illustrate that a macroscopic material is made up of many atoms of the same element. Additionally, it introduces the periodic table as a catalog of known elements and explains how to read the atomic number and atomic mass from the table, which represent the number of protons and the total number of protons and neutrons, respectively.

The second paragraph delves deeper into the atomic structure, explaining how to determine the number of protons, electrons, and neutrons from the periodic table. It uses beryllium as an example to demonstrate the calculation process. The paragraph clarifies that the atomic number corresponds to the number of protons, which is usually equal to the number of electrons, and the atomic mass is the sum of protons and neutrons. It also touches on the concept of electron energy levels, explaining that the first energy level can hold up to two electrons, making it stable when full.

This paragraph continues the discussion on electron energy levels, explaining that the second energy level can hold up to eight electrons for stability. It uses helium, neon, and argon as examples to illustrate atoms with full energy levels, which are considered stable. The paragraph then introduces the concept of atomic instability when the outermost electron level is not full, as exemplified by carbon, which has only four electrons in its second level, requiring four more to be stable. The paragraph sets the stage for discussing chemical bonds, which form when atoms are not stable and seek to achieve stability by sharing or transferring electrons.

The fourth paragraph focuses on covalent bonds, where atoms share electrons to achieve stability. It uses the molecule of oxygen (O2) as a prime example, explaining that each oxygen atom shares two electrons with another oxygen atom, resulting in a stable molecule with eight electrons in each atom's outer level. The paragraph also describes the process of electron sharing visually, likening it to an 8-shaped motion between the two atoms, and explains that this sharing results in a double bond, represented by two dashes in chemical notation.

The final paragraph introduces ionic bonds, which occur when one atom gains or loses electrons, creating charged particles known as ions. It contrasts this with covalent bonds, where electrons are shared. The paragraph uses the example of sodium chloride (table salt) to explain how sodium, with one electron in its outer level, loses that electron to chlorine, which needs one more electron to fill its outer level. This transfer results in a positively charged sodium ion and a negatively charged chloride ion, which are attracted to each other due to their opposite charges, forming an ionic bond. The paragraph concludes with a brief explanation of how the loss and gain of electrons change the atomic structure and net charge of the atoms involved.