Before we talk about the atom, we should be looking at the evidences scientists discovered through the years.
An atom is the basic unit of an element. An atom is a form of matter which may not be further broken down using any chemical means
Atoms are composed by many particles, we will concentrate in the main ones: Protons, neutrons and electrons.
- The atoms of the same element all have the same number of protons.
- The atoms of different elements have different numbers of protons
- PROTONS and NEUTRONS are located in the NUCLEUS
- These are the only HEAVY particles in the atom.
HOW MORE MASSIVE?
What you need to know for your exam:
ATOMIC NUMBER (Z) AND MASS NUMBER (A) – ISOTOPES
ATOMIC NUMBER (Z): The amount of protons in the nucleus gives the element its identity and properties, that’s why it is called atomic number
ATOMIC MASS(A): (ALSO CALLED NUCLEON NUMBER) It’s the total amount of particles in the nucleus. (Protons + Neutrons)
ISOTOPES: Atoms MUST HAVE the same number of protons if they belong to the same element, but they can also have DIFFERENT amount of neutrons. these different variations of the same element are called isotopes
Atoms with more or less electrons in the electron cloud are called IONS. We have to show the charge when we represent the ion indicating if it is negative, positive and how many charges it has.
HOW DO WE REPRESENT ATOMS?
The picture shows: X as the element, the zone where we need to indicate the mass and atomic number, so as to the charge of the ion (if any).
Behavior of protons neutrons and electrons in an electric field
ELECTRONS are attracted to the positive pole since they have a negative charge
PROTONS are deflected towards the negative pole since they carry a positive charge
NEUTRONS are no deflected since they have no charge so they are no attracted or repelled by the electric field
ELECTRONS are MORE deflected than PROTONS since electrons have a smaller mass