Explaining the Periodic Table (6.7) If elements are the building blocks of all other matter, what are they made of? There are three particles that make up an atom or element: protons electrons neutrons These are called subatomic particles because they are smaller or below an atom.

PROTONS are located in the nucleus and have a positive charge. NEUTRONS are also located in the nucleus and have no charge. ELECTRONS are located in orbits around the nucleus. They have a negative charge.

Explaining the Periodic Table (6.7) How many ELECTRONS, PROTONS and NEUTRONS are in an atom? C carbon element symbol element name atomic number atomic mass (mass number)

Atomic Number C carbon atomic number atomic number = # of protons each element has a unique atomic number each element is identified by its atomic number and number of protons (ex. the element carbon, and only carbon, has the atomic number of 6) In a neutral atom, the number of positives must equal the number of negatives. This means the # of electrons = # of protons

Atomic mass (mass number) atoms of an element may have different masses because they have different numbers of neutrons – these are called isotopes round mass to a whole number C carbon atomic mass (mass number) mass number = sum of protons + neutrons

From the atomic number and mass number of an atom, we can determine the number of protons, electrons, and neutrons in an atom. # protons = atomic number # electrons = # protons (for neutral atoms only) # neutrons = mass number – atomic number Ex) Determine the number of protons, electrons and neutrons in the following atoms: a) Fluorine b) Bromine c) Sodium ____ protons ____ protons ____ protons ____ electrons ____ electrons ____ electrons ____ neutrons ____ neutrons ____ neutrons

Bohr-Rutherford diagrams are drawings of atoms that show the number of protons and electrons in the nucleus and the number of electrons in each energy level (orbit). Ex) 1 st orbit can hold 2 electrons The 2 nd and 3 rd orbits can hold 8 electrons

Let’s try drawing Bohr-Rutherford Models: 1 H Hydrogen 1 0 1

5 B Boron

10 Ne Neon

13 Al Aluminum

16 S Sulphur

19 K Potassium