Chapter 2: The STRUCTURE of the ATOM

Learning outcomes:  Sub-atomic particles (protons, neutrons and electrons), Isotopes  Structure of the atom  Behavior of sub-atomic particles in electric fields

English check  Atom  Molecule  Proton  Neutron  Electron  Isotope  Electric field  Positive charge  Negative charge  Nucleus  Deflection  Positive ion  Negative ion  Beam  Periodic table of elements  Nucleon  Relative atomic mass  Subatomic particle

Check  Deflection  Positive ion  Negative ion  Beam  Periodic table of elements  Nucleon number  Mass number  Atom number  Relative atomic mass

proton neutron electron Since 1932 we know that atoms are made from smaller subatomic particles. There are three types of subatomic particles:

Inside the Atom: a labelled diagram of the atom with: the nucleus, protons, neutrons and electrons. nucleus neutron proton electron Which element does this diagram represent?

Particle Symbol Relative mass Relative charge electron e 0 neutron n 10 proton p 1+1

How do we know the charge of subatomic particles? From experiment to knowledge

Deflection of sub-atomic particles

The behavior of protons, neutrons, and electrons in electric field  Protons are positively charged and so would be deflected on a curving path towards the negative plate.  Electrons are negatively charged and so would be deflected on a curving path towards the positive plate.  Neutrons don't have a charge, and so would continue on in a straight line.

Check!

Example: Boron B boron From the table of elements we can not see how many isotopes an element has Symbol of the element Name of the element Proton or atomic number Relative atomic number (Ar)

Boron has 2 isotopes 5B5B5B5B Question: how many % of the boron atoms is B-10 and how many % is B-11? “Boron-10” or “Boron-11” or

Atomic- and mass number  Proton- or Atomic number (Z) is the number of protons in the nucleus of an atom  Nucleon- or Mass number (A) is the sum of protons and neutrons in the nucleus of an atom.  Z X with X the symbol for the element. e.g. 4 Be, 6 C, 12 Mg A

Number of protons = Z Number of neutrons = Number of electrons = Z or >Z or <Z How many?? Number of protons + neurons = A A - Z For “ion” the number of proton is NOT the same as electrons

 Find the number of protons, neutrons and electrons in each of these neutral elements:  Find the number of protons, neutrons and electrons in each of these ions: 12 Mg Na + 17 Cl - O

Isotopes  Isotopes are atoms with the same number of protons but different number of neutrons.  17 Cl and 17 Cl Smart instrument 3537 We can now determine the “relative atomic mass” of the Cl- atom

Isotopes The hydrogen atom has 3 isotopes

Isotopes Which one of these statements best describes isotopes? A Atoms of the same element with different numbers of neutrons B Atoms of different elements with different numbers of nucleons C Atoms of the same element with different numbers of electrons D Atoms of different elements with the same number of nucleons

 Elements: which can not be broken down further into simpler substances by chemical means. Or contain only one type of atom.  A tiny region in the center of the atom is called nucleus (pl. nuclei)  Proton: a subatomic particle with a relative mass of 1 and a charge +1 found in the nucleus of all atoms.  Neutron: an uncharged subatomic particle present in the nuclei of atoms – a neutron has a mass of 1 relative to a proton. Vocabulary

 Electron: a subatomic particle with negligible mass and a charge of -1.  The nucleus is made up of particles called nucleons (protons and neutrons)  Each shell is a certain distance from the nucleus at its own particular energy level.