Chemical and metallic bonding

SCIENCE IN ACTION

By MICHAEL JOHN UGLO
THIS is the third lecture in the Science in Action series and it is on chemical and metallic bonding.
See, science education is very paramount to develop the human resource in this country. The idea to create assets and resources and products to trade with the world will only happen when we produce scientists and mathematicians who will take the task to map out very necessary parameters paramount to create those resources. Without science education, we may lose big time. Science resources such as text books, equipment and manpower to spearhead the task would be very necessary to give a start now and right away.
In chemical and metallic bonding, the principal matter involved are the atoms of elements. An atom is made of three sub-atomic particles called the protons which carry positive charges, electrons, negative charges and the neutrons carrying no charges. Protons and neutrons make up the nucleus of an atom and they give the atomic mass.

The protons alone give the atomic number. The number of protons and electrons are equal so the charges are balanced to make every atom of an element neutral. Electrons are arranged in shells called the energy levels. They are arranged in layers called the K,L,M,N and O shells around the nucleus. These shells allow for certain maximum number of electrons before they are full. The first shell (K shell) requires a maximum of two electrons for it to be full. The next shell (L shell) requires a maximum of eight electrons before it is full followed by the M shell requiring a maximum of 18 electrons and then N shell 32, O shell 64 electrons and so on.
After this, the arrangement gets complicated with electron orbitals and electron spins. The arrangement is 2,8,8,18,36 and 64.
Chemical reactions take place all the time when electrons and protons are left alone because they always combine or react chemically to form new products. This is a chemical change unlike the physical changes where no new substances are formed. Always two chemical bonds occur in chemical bonding. These are called the ionic bonds and the covalent bonds.
Covalent bonds are formed by the sharing of electrons from two atoms. These are always two different atoms of two non-metals sharing their electrons to form a molecule of a different chemical compound.
For instance, water is formed from sharing of electrons from atoms of hydrogen and atoms of oxygen which are two different non-metallic elements. One electron each from two atoms of hydrogen combine with two electrons from one atom of oxygen to give a molecule of water. This is shown in its chemical formula which is H2O. Hydrogen and oxygen are gaseous elements but chemically react or chemically combine to produce a water molecule.
In ionic bonding, electrons of two different elements get transferred or donated and accepted to form compounds called the ionic compounds. This time a metallic element which donates its valence electrons and a non-metallic element which accepts into its valence electrons what is donated by the metallic element to form the ionic compounds. The group 1,2 and 3 elements are metallic elements with the numbers I, 2 and 3 referring to the electrons in their outer most shell to donate or transfer. When they do that they form positive ions called cations. The group 5, 6 and 7 elements have 5, 6 and 7 valence electrons in their outer most shells to accept 3, 2 or 1 electron to attain a full octet shell of 2, or 8 electrons. When they do that, they form negative ions called anions. The ionic compounds’ smallest building blocks are called formula units. For example, the ionic bond between sodium and chlorine produces the formula unit sodium chloride called the table salt.

The Group 4 elements are called transition metals because they have four valence electrons in their outer most shells. Therefore, are grouped in the middle of the periodic table (Group 4). Hence, they neither donate nor accept electrons but form covalent compounds by sharing their valence electrons with other elements. The covalent compounds’ smallest building blocks are called molecules. For example, the covalent bond between hydrogen and oxygen gas produces molecules of water.
Metallic bonding is bonding between metallic elements due to strong forces seen in positive ions in metals called electrostatic attraction and the sea of electrons called the delocalized electrons found in the metallic element.
The group 1-7 elements on the periodic table all react to produce new products called compounds of formula units or molecules depending on whether they are covalent bonds or ionic bonds. The group eight elements are all gases called noble gases because they are nonreactive or inert. These inert gases’ outermost electrons or valence electrons are full. For instance, helium has a full electron of 2 in its outer most shell, neon 2, 8, and 8 is outer most shell full, argon 2,8,8, is also full octet shell and krypton has its outer most shell full with 18 electrons with its arrangement 2,8,8,18.
My Prayer for PNG today is: “To share in His suffering. Like Him in His death. All treasure is worth the price of knowing Him … All I want, is to know and love my Lord…”
Next week: Metals, non-metals and their compounds.

• Michael Uglo is the author of the science textbook “Science in PNG, Pacific, Asia and Caribbean” and a lecturer in avionics, auto- piloting and aircraft engineering. Please send comments to: [email protected]