Describe the arrangement of subatomic particles (electrons, protons, neutrons) in elements

Elements are defined as substances that consist of one type of atom, for example Carbon atoms make up diamond, and also graphite. Pure (24K) gold is composed of only one type of atom. Atoms are the smallest particle into which an element can be divided. The ancient Greek philosophers developed the concept of the atom, although they considered it the fundamental particle that could not be broken down. We now know that the atom is divisible, often releasing tremendous energies as in nuclear explosions or (in a controlled fashion in) thermonuclear power plants.

Subatomic particles were discovered during the 1800s. For our purposes we will concentrate only on three of them.

The proton is located in the center (or nucleus) of an atom, each atom has at least one proton. Protons have a charge of positive one, and a mass of approximately 1 atomic mass unit (amu). Elements differ from each other in the number of protons they have, e.g. Hydrogen has 1 proton; Helium has 2.

The neutron also is located in the atomic nucleus (except in Hydrogen). The neutron has no charge, and a mass of slightly over 1 amu. Some scientists propose the neutron is made up of a proton and electron-like particle.

The electron is a very small particle located outside the nucleus. Because they move at speeds near the speed of light the precise location of electrons is hard to pin down. Electrons occupy orbitals, or areas where they have a high statistical probability of occurring. (An orbital is also an area of space in which an electron will be found 90% of the time).The charge on an electron is -1. Its mass is negligible (approximately 1800 electrons are needed to equal the mass of one proton).

The atomic number is the number of protons an atom has. It is characteristic and unique for each element. The atomic mass (also referred to as the atomic weight) is the number of protons and neutrons in an atom. Atoms of an element that have differing numbers of neutrons (but a constant atomic number) are termed isotopes.


¥ Bohr Model of elements 1 to 20 (atoms and ions)

Read Page 170 of Science Probe 10 to page 172 then use the Periodic Table on Page 516 & 517 to draw the Bohr ModelÕs for:

H, He, Li, Be, B, C, N. O. F. Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K & Ca.

            (You can check your work by looking at page 196 of Science Probe 10.)


¥ Bohr Model of simple ionic and covalent compounds using elements 1 to 20

A chemical compound is a substance made of two or more elements combined in a definite formula. Every compound has its own chemical formula, which shows the proportion of elements present in that compound.

See Figure 9.10 (Page 194),  See Figure 9.13 (Page 196), See Figure 9.15 (Page 199) and Figure 9.16 (Page 201) for examples of Bohr Models of simple ionic compounds. See Figure 9.21 & 9.22 (Page 206) for Bohr Models of simple covalent compounds.