Atom The basic building block of all matter. Came from the Greek word átomos: undivided Material from:

A. Parts of an Atom 1. Nucleus: in the center of an atom a. Protons: Positively charged particles Positively charged particles Have the mass of 1 atomic mass unit (1 amu) Have the mass of 1 atomic mass unit (1 amu) b. Neutrons: Neutrally charged particles (no charge) Neutrally charged particles (no charge) Also have mass of 1 amu. Also have mass of 1 amu. p+p+ n

A. Parts of an Atom (continued) (continued) 2. Electron Cloud: 2. Electron Cloud: a. The place outside the nucleus that a. The place outside the nucleus that you’ll most likely find an electron you’ll most likely find an electron b. Electrons: b. Electrons: Negatively charged particles Negatively charged particles Have VERY little mass (1/2000 amu) so it’s not included in an atom’s mass. Have VERY little mass (1/2000 amu) so it’s not included in an atom’s mass. e-e-

B. Atomic Number 1. The number of protons in an atom. 2. It makes each element unique. 3. It’s the smaller whole number in an element’s box. 4. When drawing an atom diagram, we usually draw the same number of electrons as protons. 5. What is the atomic number of each element and how many protons & electrons are in each??

C. Atomic Mass 1. It’s the sum of the protons and neutrons in an atom. Atomic Mass = (atomic number) + (# of neutrons) Atomic Mass = (atomic number) + (# of neutrons) 2. Number of neutrons = (atomic mass) – (atomic number) rounded rounded 3. The unit is: amu (for atomic mass unit). 4. What’s the atomic mass of each element below? 5. How many neutrons are in each element below?

Open to your “Atoms” notes and copy this: A Diagram of a Nitrogen Atom 7 N Nitrogen Atomic Number : Equal to number of protons in one atom, as well as electrons Atomic Mass : Comes from total mass of protons+neutrons (electrons add very little mass) Element Symbol Element Name ++n +nn+n +n+n+ n Nucleus area: Protons (+) & Neutrons (n) 1 st Electron Shell: can hold 2 -e 2 nd Electron Shell: can hold 8 -e Electrons (-e) - e

D. Periodic Table of the Elements 1. This lists all elements, by atomic number

Summary – Important Things to Remember Atoms contain: Atoms contain: 1.Protons (+): They have a positive charge. Atomic mass = 1 amu Atomic mass = 1 amu # of Protons = Atomic Number # of Protons = Atomic Number 2.Neutrons (n): They have a neutral charge. Atomic mass = 1 amu Atomic mass = 1 amu # of Neutrons = (Atomic Mass) – (Atomic #) # of Neutrons = (Atomic Mass) – (Atomic #) 3. Electrons (-): They have a negative charge. Very small mass & are located in different energy level shells Very small mass & are located in different energy level shells # of Electrons = Number of protons # of Electrons = Number of protons

D. Atom Bonds 1.Covalent Bonds Electrons are shared between atoms Electrons are shared between atoms Example: Water molecules are made from 2 Hydrogen atoms and 1 Oxygen Atom. Each Hydrogen atom has 1 electron. They are then shared with the Oxygen atom because it can hold 2 more electrons in its outside 2nd shell. Example: Water molecules are made from 2 Hydrogen atoms and 1 Oxygen Atom. Each Hydrogen atom has 1 electron. They are then shared with the Oxygen atom because it can hold 2 more electrons in its outside 2nd shell. 2. Ionic Bonds Electrons are transferred from one atom to another Electrons are transferred from one atom to another Example: To make table salt (chemically called Sodium Chloride), a Sodium atom gives/transfers its 1 electron that is in its 3rd electron shell to a Chlorine atom. Sodium is happy as its outside 2nd shell is full with 8 electrons. Chlorine’s 3rd shell has 8 electrons and is also happy. Example: To make table salt (chemically called Sodium Chloride), a Sodium atom gives/transfers its 1 electron that is in its 3rd electron shell to a Chlorine atom. Sodium is happy as its outside 2nd shell is full with 8 electrons. Chlorine’s 3rd shell has 8 electrons and is also happy.

1. Covalent Bonds

1. Covalent Bonds (con’t)

Atom Bonds 2. Ionic Bonds Electrons are transferred from one atom to another Electrons are transferred from one atom to another Example: To make table salt (chemically called Sodium Chloride), a Sodium atom gives/transfers its 1 electron that is in its 3rd electron shell to a Chlorine atom. Sodium is happy as its outside 2nd shell is full with 8 electrons. Chlorine’s 3rd shell has 8 electrons and is also happy. Example: To make table salt (chemically called Sodium Chloride), a Sodium atom gives/transfers its 1 electron that is in its 3rd electron shell to a Chlorine atom. Sodium is happy as its outside 2nd shell is full with 8 electrons. Chlorine’s 3rd shell has 8 electrons and is also happy.

2. Ionic Bonds n n