Atomic structure-basics
An atom is the smallest part of an element that still has the properties
of that element. Everything in the world is made of atoms.
Atoms have 3 subatomic particles protons, neutrons, and electrons.
• Protons have a charge of positive 1 and have a mass of 1. The proton
is found in the nucleus.
• Neutrons have a charge of 0/neutral and have a mass of 1. the
neutron is found in the nucleus.
• Electrons have a charge of negative 1 and have a mass of 1/1840. The
electrons are found on the shells of the atoms.
Atoms have 2 numbers atomic number and mass number.
• Atomic number is the bottom left number and represents the number
of protons in the atom.
• Mass number is the top right number and show the number of
protons and neutrons in the nucleus.
• To find the number of electrons in an atom you just look at the atomic
number because for an atom to have a neutral charge the protons
and electrons must be equal.
Electronic shells
Electrons are arranged in shells around the nucleus
• The first shell can carry a max of 2 electrons
• The second and third shells can carry a max of 8 electrons
• You fill the shells from closest to nucleus to furthest from the
nucleus [ shell 1] to the outer shells [ shells 2 and 3]
Key terms
• Isotopes are atoms with the same number of protons but different
numbers of neutrons
An atom is the smallest part of an element that still has the properties
of that element. Everything in the world is made of atoms.
Atoms have 3 subatomic particles protons, neutrons, and electrons.
• Protons have a charge of positive 1 and have a mass of 1. The proton
is found in the nucleus.
• Neutrons have a charge of 0/neutral and have a mass of 1. the
neutron is found in the nucleus.
• Electrons have a charge of negative 1 and have a mass of 1/1840. The
electrons are found on the shells of the atoms.
Atoms have 2 numbers atomic number and mass number.
• Atomic number is the bottom left number and represents the number
of protons in the atom.
• Mass number is the top right number and show the number of
protons and neutrons in the nucleus.
• To find the number of electrons in an atom you just look at the atomic
number because for an atom to have a neutral charge the protons
and electrons must be equal.
Electronic shells
Electrons are arranged in shells around the nucleus
• The first shell can carry a max of 2 electrons
• The second and third shells can carry a max of 8 electrons
• You fill the shells from closest to nucleus to furthest from the
nucleus [ shell 1] to the outer shells [ shells 2 and 3]
Key terms
• Isotopes are atoms with the same number of protons but different
numbers of neutrons
