1.1 atoms

• Atoms are made up of tiny particles called Electrons and Protons and Neutrons
• A single cell contains more than 100 trillion atoms
• Each atom is made up of a central nucleus surrounded by electrons in shells
• The nucleus is made up of protons and neutrons
• Electrons orbit around the nucleus in shells
• Protons and neutrons have the same mass, which is a relative mass of one
• Electrons are much smaller and have a mass 2000 times smaller than protons and neutrons
• Protons have a positive charge of one plus
• Neutrons have no charge and are neutral
• Electrons have a negative charge of minus one
• Atoms have a radius of around 0.1 nanometers
• Most of an atom is empty space
• The nucleus is 10,000 times smaller than the atom itself
• Atoms can lose or gain electrons, becoming ions
• An atom becomes an ion when the charges no longer balance
• The periodic table represents different types of atoms called elements
• Each box in the periodic table represents an element
• The elemental symbol represents the element, e.g., O for oxygen and Li for lithium
• The atomic number tells us how many protons an atom of that element has
• The mass number tells us the total number of neutrons and protons in an atom
• The number of protons in an atom determines which element it is
• The number of protons and electrons in an atom is always the same
• The atomic number also tells us how many electrons an atom has