Atoms

• Atoms are the smallest units of matter made up of protons, neutrons and electrons.
• The nucleus, central part of an atom, contains protons and neutrons. The electrons move around the nucleus.
• Protons are positively charged particles. The atomic number of an atom corresponds to the number of protons in the nucleus.
• Neutrons are neutral particles, carrying no charge. The mass number of an atom corresponds to the combined total of protons and neutrons in the nucleus.
• Electrons are negatively charged particles which move around the nucleus in energy levels or shells. An atom is neutral because the positive charge of the protons balances with the negative charge of the electrons.
• Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different mass numbers.
• The electronic structure of an atom refers to the arrangement of electrons in shells. The first shell can hold up to 2 electrons, the second can hold up to 8 electrons, and so on.
• Elements are pure substances composed of only one kind of atom.
• The Periodic Table is used to organise and classify the elements based on increasing atomic number and chemical properties. Elements in the same group (column) have similar chemical properties and the same number of electrons in their outer shell.
• Chemical reactions involve the rearrangement of atoms. These atoms can’t be created or destroyed during a chemical reaction.
• The study surrounding atoms and atomic structure is fundamental to understanding chemical reactions, the properties of matter, and the characteristics of elements on the Periodic Table.