1. Elements Isotopes and Ions

2. Current atomic model
An atom is mostly empty space surrounding a tiny nucleus
Nucleus contains protons (positively charged particles) and neutrons (particles with no charge)
An electron is a negatively charged particle that moves in the space surrounding the nucleus

3. Elements
Elements are pure substances made from atoms that all have the same number of protons
Number of protons in the atom of an element is the element’s atomic number

4. Atomic number and the periodic table
How can you find out how many protons an element has if you don’t know the atomic number? You use the periodic table of elements.
How to solve for protons?
Atomic number = # of protons

5. Finding the number of electrons
Atoms have no overall electrical charge
There must be a balance between the positively charged protons and negatively charged electrons
# of protons = # of electrons

6. Atomic mass and mass number
Atomic mass is the weighted average mass of the mixture of the element’s isotopes.
Each proton has a mass of 1 amu
Each neutron has a mass of 1 amu
Electrons are so small that they have a mass unit of almost zero
Mass number is the sum of the number of protons and neutrons
You can find the number by rounding the atomic mass
Protons + Neutrons = mass number

7. Finding the number of neutrons
You round the atomic mass and subtract the atomic number to solve for the number of neutrons

8. Isotopes – Different numbers of neutrons
The nucleus contains protons and neutrons
Atoms of the same element ALWAYS have the same number of protons…
However, atoms of the same elements SOMETIMES have different number of neutrons
These are called ISOTOPES

9. Isotopes
Isotopes – atoms that have the same number of protons but different number of neutrons
Each element has a limited number of isotopes that occur naturally
Some can be radioactive (pg 199)

10. Using Isotopes
Radioactive isotopes have unstable nuclei that break down and release particles, radiation and energy
This can be used for dating bones, determining ages of rocks and fossils, diagnose and treat many medical conditions

11. Ions – gaining or losing electrons
Atoms are neutral because the number of protons (+) and electrons (-) are equal
However, atoms can lose or gain electrons
This means the atom is no longer neutral and has become an ion
Ion is an atom that has gained or lost electrons