Basic Chemistry CHAPTER 2

Video 

What are elements?  What can you tell me about elements?

What are elements?  Elements: The fundamental units of matter

What are elements?  Elements: The fundamental units of matter  What do we mean by fundamental?

What are elements?  Elements: The fundamental units of matter  What do we mean by fundamental?  Necessary base or core

Elements of the Body  96% of the body is made from 4 different elements

A Look at Matter

Elements of the Body  96% of the body is made from 4 different elements  Carbon (C)  Oxygen (O)  Hydrogen (H)  Nitrogen (N)

Hydrogen Bomb  

What are atoms?

 Atoms: The building blocks of elements

Atomic Structure  What are the different parts of an atom?

Atomic Structure  Nucleus  Protons (p + )  Neutrons (n 0 )  Outside of nucleus  Electrons (e - )

Atomic Structure of Smallest Atoms



How do we identify elements?

 Atomic number

How do we identify elements?  Atomic number: equal to the number of protons that the atom contains

How do we identify elements?  Atomic mass number:

How do we identify elements?  Atomic mass number: sum of the protons and neutrons

 Why are atomic masses not in whole numbers?  Protons + Neutrons right?

Isotopes and Atomic Mass  ISOTOPES!

Isotopes and Atomic Mass  Isotopes:  Have the same number of protons  Vary in number of neutrons

Isotopes and Atomic Mass  Close to mass number of most abundant isotope  Atomic weight reflects natural isotope variation

Isotopes and Atomic Mass  otopes-and-atomic-mass

Electrons and Bonding  Energy levels called electron shells  Electrons closest to the nucleus are most strongly attracted

Electrons and Bonding  Bonding - interactions between electrons in the outer shell (valence shell)  Full valence shells do not form bonds

Electrons and Bonding  How to fill the atom’s shells  Shell 1 - maximum of 2 electrons  Shell 2 - maximum of 8 electrons  Shell 3 - maximum of 18 electrons  Shell 4 - maximum of 32 electrons  Shell 5 - maximum of 50 electrons  Shell 6 – maximum of 72 electrons

Electrons and Bonding

Lewis Dot Structures  Diagrams that show the bonding between atoms  Represent the valence shell  Carbon has 6 protons, 6 elections  So…….4 electrons are in the valence shell

Lewis Dot Structures

Rule of Eights (Octet Rule)  Atoms are considered stable when their outermost orbital has 8 electrons  The exception to this rule of eights is Shell 1, which can only hold 2 electrons  mx_14E mx_14E

Electrons and Bonding  e/add_ocr_gateway/periodic_table/atomstrucact.s html e/add_ocr_gateway/periodic_table/atomstrucact.s html

Radioactivity  Radioactivity—process of spontaneous atomic decay  What can we use this for?

Radioactivity  Radioactivity—process of spontaneous atomic decay  What can we use this for?

Radioactivity  Radiometric Dating:  Uranium  238 U to 206 Pb, with a half-life of 4.47 billion years  235 U to 207 Pb, with a half-life of 704 million years.  Carbon  Carbon-14 is a radioactive isotope of carbon, with a half-life of 5,730 years  Very short compared to other isotopes

Molecules and Compounds  Molecule: Two or more like atoms combined chemically  Compound: Two or more different atoms combined chemically

Molecules and Compounds

What are chemical reactions?  What do you remember?

What are chemical reactions?  Atoms are united by chemical bonds OR  Atoms dissociate from other atoms when chemical bonds are broken