Do Now: You may use your notes 1. Who discovered protons and the nucleus? 2. Who discovered electrons and proposed the plum pudding model? 3. Who proposed the 1 st atomic model? 4. Who proposed the theory of electron clouds? 5. Who discovered neutrons? 6. Who proposed the model with electrons travelling in orbits around the nucleus? 7. Who was the father of modern chemistry? 8. Who proposed the first scientific atomic theory?

The Quantum Mechanical Model The NucleusThe Electron Cloud

The Nucleus O The nucleus is the positively-charged core at the center of an atom. O It is TINY in comparison to the whole atom. If the atom is the size of a football field, the nucleus is a nickel in the middle of the field. O It is VERY dense--within this tiny space, the nucleus contains 99.97% of the atom’s mass. O It contains the protons and neutrons.

The Electron Cloud O The electron cloud is the negatively-charged region surrounding the nucleus of an atom. O It is VERY BIG in comparison to the whole atom. If the atom is the size of a football field and the nucleus is a nickel in the middle of the field, the electron cloud is the rest of the field. O It is NOT VERY dense at all--within this large space, the nucleus contains only 0.03% of the atom’s mass. O It contains the electrons. (DUH!)

Elements O So far we have learned that an element is a pure substance that cannot be broken down into any simpler substances O What can you look at to find all of the elements that exist in our world? O Another way to think of an element is that it is an atom with a specific number of protons.

How to Read the Periodic Table Element Name Atomic Number (# of protons) Element Symbol Atomic Mass

Atomic Numbers O Atomic Number = #of Protons O Mass Number= # of Protons + # of Neutrons O So # of neutrons= mass - # protons O Atomic Number usually equals # of electrons

Look at Beryllium O How many protons does it have? O How many electrons does it have? O How many neutrons does it have?

Which element has 12 protons? O How many electrons does it have? O How many neutrons?

Bohr Models O Niels Bohr developed the Bohr model of atoms. O This model looks like a solar system and is special because it uses energy levels. Based on the number of protons, this is a Bohr model for Carbon!

Bohr Model O What subatomic particles are in the nucleus? O What subatomic particle is on the energy levels around the nucleus? O Each energy level can hold a specific number of electrons: Energy Level #1234 # e-’s that Fill

Calculating Charge of an Atom O What is the charge of this atom? Count the number of protons. Subtract the number of electrons. This is the charge.

On Your Own! O Draw a Bohr model for an atom that has 4 protons, 5 neutrons, and 4 electrons O What element is this? O What is the charge of this atom? O Draw a Bohr model for an atom that has 13 protons, 14 neutrons, and 14 electrons O What element is this? O What is the charge of this atom?

On Your Own! O Draw a Bohr model for an atom that has 2 protons, 2 neutrons, and 2 electrons O What element is this? O What is the charge of this atom? O Draw a Bohr model for an atom that has 10 protons, 10 neutrons, and 10 electrons O What element is this? O What is the charge of this atom?

Recap: Calculating Subatomic Particles O # of protons = atomic number O # of electrons = atomic number O # of neutrons = atomic mass – atomic number

Atomic Notation O How do scientists write element names?

Nuclear Notation Mass Number Atomic Number

Nuclear Notation

O Fill in the table for the following atoms: O A lithium atom with a mass number of 7 O An atom with 7 protons and a mass number of 14 O An atom with 22 electrons and a mass number of 47 O A platinum atom with a mass number of 194 O An arsenic atom with a mass number of 75

Isotope Notation O Isotope notation is even easier! NAME OF ELEMENT – mass #

Comparing Nuclear and Isotope Notation O How are they similar? O How are they different?

Calculating Mass Number O Because an atom is so small, we have a special unit to represent its mass. O The mass of an atom is found in atomic mass units, or amus. ProtonElectronNeutron Mass 1 amu0 amu1 amu

Calculating Mass Number

On Your Own! O Calculate the masses of Fluorine, Sodium, and Zinc (Examples 7-9).