The Periodic Table
The Periodic Table
Basic Concepts
- The Periodic Table is a chart illustrating elements in increasing order of their atomic numbers.
- It consists of rows called periods and columns called groups.
- An element’s position in the table indicates its physical and chemical properties.
Atomic Structure
- The atomic number represents the number of protons in an atom’s nucleus.
- Atomic mass, meanwhile, is the total number of protons and neutrons.
- Elements in the same group have the same number of electrons in their outer shell, also referred to as valence electrons.
Groups
- Group 1 elements, the alkali metals, are highly reactive metals with 1 electron in their outer shell.
- Group 2 are the alkaline earth metals. They have 2 electrons in their outer shell and are less reactive than Group 1.
- Group 7 includes the halogens, non-metals that are very reactive and have 7 electrons in their outer shell.
- Group 0 includes noble gases, chemically unreactive gases with full outer shells.
Periods
- The number of shells of electrons around an atom’s nucleus is indicated by its period number.
- Elements in the same period have the same number of electron shells.
Blocks
- Elements are also categorised into blocks (s, p, d, and f blocks) based on the type of orbitals that the outermost or valence electrons occupy.
Periodic Trends
- Moving left to right across periods, atomic size generally decreases while ionisation energy generally increases.
- These trends reverse when moving top to bottom down groups: atomic size generally increases and ionisation energy generally decreases.
Transition Metals
- Grouped in the middle of the Periodic Table, transition metals have similar properties like being hard and having high melting points.
- They form coloured compounds and have variable oxidation states.
Understanding Patterns
- Patterns in properties and reactions of elements are predicted by their position in the Periodic Table.
- For example, the reactivity of the alkali metals increases down the group.
Misconceptions about the Periodic Table
- Not all elements are solid at room temperature; Bromine is a liquid and the noble gases are gases.
- The appearance of an element does not predict its properties; lead and gold look similar but have different properties.