When Atoms Change…

What we KNOW… Atoms on the periodic table are neutral. Atoms are neutral because they have the same number of protons as electrons. protons have a positive charge. neutrons have no charge. electrons have a negative charge.

What we Also need to KNOW… The identity of an atom is determined ONLY by the number of protons. For example… If I tell you there is an atom with 3 protons… you know it’s a Lithium atom. What about 8 protons, 13 protons, 79 protons???

What happens if the number of neutrons change??? If an atom gains neutrons… 1. The mass increases by 1 for every neutron added. 2. The number of protons and electrons stay the same. 3. The charge remains neutral. (Neutrons don’t have a charge.) 4. The identity of the atom does not change If an atom loses neutrons… 1.The mass decreases by 1 for every neutron taken away. 2.The number of protons and electrons stay the same. 3.The charge remains neutral. (Neutrons don’t have a charge.) 4.The identity of the atom does not change

What happens if the number of neutrons changes??? But when we compare the same types atoms with different masses we are comparing isotopes!. Only the mass changes! I sotope: Same kind of atom but with a different number of neutrons

ISOTOPE EXAMPLE Most commonly occurring hydrogen isotope Has a mass of 1 and an atomic number of 1 Less commonly occurring hydrogen isotope Has a mass of 2 and an atomic number of 1

ISOTOPE NOTATION We communicate that we are talking about a specific isotope by using the Atomic Symbol of the isotope followed by the “NEW” mass number. For Example: The most common isotope of lithium is: Li 7

Isotope INVENTORY Completing a particle inventory for an Isotope is almost the same as the neutral atom EXCEPT we USE THE “NEW” MASS NUMBER to calculate neutrons. Ex: Li-6 3p+ (since it’s Lithium!!!) 3e- (since they are still equal to p+) 3n

Isotope Practice Ca atom has a mass of 40. The isotopes for Ca are: Ca-42, Ca-43, Ca-44, Ca-46, & Ca ) How many neutrons are in a Ca atom and each of its isotopes? 2.) What are the differences and similarities between the Ca atom and its isotopes?

Isotope Practice Ca atom has a mass of 40. (atomic # or #of P + ’s = 20) The isotopes for Ca have masses of 42,43,44,46, & 48. To find the number of neutrons you subtract the atomic number from the mass number. 1.) How many neutrons are in a Ca atom and each of its isotopes? Number of Neutrons in each isotope: Ca 40 : = 20n Ca 42 : = 22n Ca 43 : = 23n Ca 44 : = 24n Ca 46 : = 26n Ca 48 : = 28n

2.) What are the differences and similarities between the Ca atom and its isotopes? Similarities: All have 20 p+, all have 20 e-, all neutral, all are Calcium Differences: The # of neutrons is different, masses are all different, nuclear stability changes.

Isotope Inventory HW Do particle inventories for each of the following isotopes: Si-30 Ar-36 Fe-54

Quiz Quick Isotopes gain or lose… A.electrons B.protons C.neutrons D.nuclei

More Isotope Practice 1.)How many neutrons are in each of Zinc’s isotopes? Zn-64____ Zn-67_____ Zn-70____ 2.) What are the differences and similarities between the Zn atom and its isotopes?

What happens if the number of electrons change??? If an atom gains electrons… 1. The mass stays the same (electron’s mass = 0). 2. The number of protons and neutrons stays the same. 3. The charge becomes negative. (There are more negative e- than positive p+ now!) If an atom loses electrons… 1.The mass stays the same (electron’s mass =0). 2.The number of protons and neutrons stays the same. 3. The charge becomes positive. (There are less negative e- than positive p+ now!)

What happens if the number of electrons changes??? The atom is now called an ION!!! Ion- An atom that has gained or lost electrons.

ION EXAMPLE H+ is a positive charged hydrogen ION Or Cation H: Is the neutral or regular hydrogen atom H- : is a negative charged hydrogen ION Or Anion