The periodic table is important as it is so well organized that it provides a lots of information about elements and how they related to one another (Figure 5).
- Systematic study of the elements
- Prediction of new elements and their properties. Mendeleev left space for the elements yet to be discovered
- Atomic mass correction of elements based on their expected positions and properties can be done easily
Element symbols in a periodic table are abbreviations of the element’s name.
In some cases, the abbreviation comes from the element’s Latin name, for example, the symbol for sodium is Na, derived from, Natrium. Most tables list element symbols, atomic number, and atomic mass (Figure 6).
The vertical columns are called groups. Each element in a group has the same number of valence electrons and typically have similar behavior when bonding with other elements.
The horizontal rows are called periods. Each period indicates the highest energy level the electrons of that element occupies at its ground state.
The bottom two rows—the lanthanides and actinide (belong to the 3B group) are listed separately.
Many periodic tables use different colors for different element types helping to identify element types.
These include the alkali metals, alkaline earths, and transition metals etc.
| Metals |
Non-metals |
|
| Appearance | Shiny | Dull |
| State at Room Temperature | Solid (except mercury, which is a liquid) | About half are solids, about half are gases, and one (bromine) is a liquid |
| Density | High (they feel heavy for their size) | Low (they feel light for their size) |
| Strength | Strong | Weak |
| Malleable or Brittle | Malleable (they bend without breaking) | Brittle (they break or shatter when hammered) |
| Conduction of Heat | Good | Poor (they are insulators) |
| Conduction of Electricity | Good | Poor (they are insulators, apart from graphite) |
| Magnetic material | Only iron, cobalt and nickel | None |
| Type of oxide | Basic or alkaline | Acidic |
Metals
Iron, magnesium, silver and gold are examples of metal elements. Metals have following properties in common.
- Shiny with exception of tin and lead.
- Good conductors of heat and electricity
- Malleable (Figure 7) as they can be bent and shaped without breaking
- Lithium (Li) is half the density of water, whereas osmium has a density 22.5 times greater than water.
- Fusible (can be melted relatively easily), except tungsten as it has melting point more than 3000o
- Metals tend to give up electrons to other elements — namely, nonmetals.
Metals, except mercury, occur as solids in nature. Three metals (iron, cobalt and nickel) are magnetic. Steel is a mixture of elements, mostly iron, so it is also magnetic. The other metal elements are not magnetic.
Non-metals
Oxygen, carbon, sulfur and chlorine are examples of non-metal elements. The most common properties of metals are as follows:
- dull
- insulators, i.e., metals are poor conductors of heat and electricity
- weak and brittle (they easily break or shatter)
- they have a low density in comparison to metals
Some non-metals, such as oxygen and chlorine, are gases at room temperature, bromine, is a liquid at room temperature and carbon (Figure 8) and sulfur are solids at room temperature.
Metalloids
Metalloids are elements with both metallic and nonmetallic properties. Silicon is an example of metalloids (Figure 9).
Electron Affinity
It is an ability to accept an electron. It can be known based on the element groups. Noble gases have an electron affinity near zero, whereas halogens have high electron affinities.
Electronegativity
It is a measure of ability to form a chemical bond.
Properties of the Elements along the Periodic Table
In a periodic table, As we move from left to right, we observe the following (Figure 6):
- Atomic radius decreases
- Ionization energy increases
- Electron affinity generally increases (except noble gas electron affinity near zero)
- Electronegativity increases
However, as we move from top to bottom, we see the following (Figure 10):
- Atomic radius increases
- Ionization energy decreases
- Electron affinity generally decreases moving down a group
- Electronegativity decreases
Most of the chemical symbols for elements in the periodic table are based on their names, however, a few seem to have no relation to their names. Some of the examples are as following:
- Sodium – Natrium (Na): Sodium’s Latin name, ‘natrium’, is derived from the Greek ‘nítron’ (a name for sodium carbonate)
- Potassium – Kalium (K): ‘Kalium’ is potassium’s Latin name, and derives from the Arabic meaning “calcined ashes” (the ashes from burned plant material)
- Iron – Ferrum (Fe): Iron’s Latin name, ‘ferrum’, gives it the symbol Fe.
- Silver – Argentum (Ag): The Latin name for silver, ‘argentum’, derived originally from an Indo-European language, likely referring to the metal’s shininess
- Gold – Aurum (Au): The Latin name for gold was ‘aurum’, meaning ‘yellow’, derived from the word ‘aurora’ (‘dawn’).