Atomic structure and the periodic table
Atomic Structure
- Atoms are made up of protons, neutrons, and electrons.
- Protons and neutrons form the nucleus of the atom in the centre, while electrons orbit in energy levels around the nucleus.
- Protons have a positive charge, electrons a negative charge, and neutrons are neutral.
- The atomic number of an atom is determined by the number of protons.
- The mass number of an atom is the total number of protons and neutrons.
- Atoms of the same element that have different numbers of neutrons are called isotopes.
Electron Configuration
- Electrons occupy energy levels or shells around the nucleus.
- The lowest energy level (closest to the nucleus) is filled first and can hold up to two electrons.
- Subsequent levels can hold up to eight electrons.
- The arrangement of electrons in an atom's energy levels is known as its electron configuration.
- The periodic table is arranged in increasing atomic number, which determines an element's electron configuration.
The Periodic Table
- The periodic table organises elements based on their atomic structure and properties.
- The table is divided into groups (vertical columns) and periods (horizontal rows).
- Elements within the same group share similar chemical and physical properties.
- The group number corresponds to the number of electrons in the outer energy level.
- The period number corresponds to the number of energy levels an atom has.
Metals, Non-Metals and Metalloids
- Elements on the left and centre of the periodic table are metals, those on the right are non-metals, and a zigzag line separates metalloids.
- Metals are typically lustrous, malleable, and good conductors of heat and electricity.
- Non-metals are typically dull, brittle, and poor conductors of heat and electricity but good insulators.
- Metalloids have properties in between metals and non-metals.
Chemical Groups
- Group 1: The Alkali Metals - These are very reactive metals that do not occur freely in nature.
- Group 2: The Alkaline Earth Metals - These are metallic elements found in the earth's crust.
- Group 7: The Halogens - These are reactive non-metals that occur naturally in various states of matter - Solid, Liquid, Gas.
- Group 0/8: The Noble Gases - These are chemically inert non-metals.