Atom Notes  – the science that studies the properties of substances and how they react with each other. Chemistry

Review Notes  Matter is made of particles called atoms that are too small to see with the eyes.  Matter can not created or destroyed.  Matter can be an element, a compound, or a mixture.

Review Notes  Elements are the simplest substances.  Matter can undergo physical and chemical changes.

How small are atoms? There are 2 x zinc and copper atoms in an ordinary penny! That is 20,000,000,000,000,000,000,000!

Types of Atoms in Earth’s Crust  Hydrogen makes up about 90% of the total mass of the universe.  In Earth’s crust,  47%Oxygen  28%Silicon  12%Other elements  8% Aluminum  5%Iron

Types of Atoms in Living Things  Living things are mostly oxygen, carbon, hydrogen, and nitrogen, plus more than 20 other elements.  In humans,  61%Oxygen  23%Carbon  10%Hydrogen  3% Nitrogen  3%Other elements

Names and Symbols of Elements  Elements get their names in different ways.  Elements can be named from people, places, and Greek words.  Each element has a unique symbol.

Elements have unique atoms  Every atom of a specific element, such as silver, is similar to every other atom of the same element.  Every atom of a specific element is different from an atom of a different element.  How? It’s all about the structure of the atom!

What is inside an atom?  Nucleus – the dense center of the atom made of protons and neutrons p p p p p p Protons Neutrons Nucleus

Let’s be positive!  Protons – positively charged particles in the nucleus: p+ p p p p p p Protons Neutrons Nucleus Protons have a mass of one amu

I don’t get a charge out of you  Neutrons - neutral particles in the nucleus: n 0 p p p p p p Protons Neutrons Nucleus Neutrons have a mass of one amu

What is on the outside?  Electrons – Negatively charged particles that orbit the nucleus in energy levels: e- p p p p p p Protons Neutrons Nucleus Electrons Shell

Neutral atoms have balance!  In neutral atoms the # of protons equals the # of electrons, but the neutrons can be different p p p p p p Protons Neutrons Nucleus Electrons Shell 5 5 4

Forces in the Atom, part 1 Gravity: pulls objects toward one another. It depends on the mass of the object and how far apart the objects are The force of gravity in atoms is very small.

Forces in the Atom, part 2 Electromagnetic Force: protons and electrons are attracted to each other because they have opposite charges

Forces in the Atom, part 3 Strong Force: protons repel each other because they have the same charge. The strong force overcomes this repulsion to hold the nucleus together.

Forces in the Atom, part 4 The Weak Force: is an important force in radioactive atoms.