basic chemistry chapter 2. what are elements? what can you tell me about elements?
TRANSCRIPT
Basic ChemistryCHAPTER 2
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?
Elements of the Body96% of the body is made from 4 different elements
What are atoms?
What are atoms? Atoms: The building blocks of elements
Atomic StructureWhat are the different parts of an atom?
Atomic Structure
NucleusProtons (p+)Neutrons (n0)
Outside of nucleusElectrons (e-)
Atomic Structure of Smallest Atoms
How do we identify elements?
How do we identify elements?Atomic number
How do we identify elements?Atomic mass number
How do we identify elements?Atomic mass number:
Why are atomic masses not in whole numbers?
Protons + Neutrons right?
Isotopes and Atomic Mass
ISOTOPES!
Isotopes and Atomic MassIsotopes:
Have the same number of protons
Vary in number of neutrons
Isotopes and Atomic MassClose to mass number of most abundant isotope
Atomic weight reflects natural isotope variation
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 shellsShell 1 - maximum of 2 electronsShell 2 - maximum of 8 electronsShell 3 - maximum of 18 electronsShell 4 - maximum of 32 electronsShell 5 - maximum of 50 electronsShell 6 – maximum of 72 electrons
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
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
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 238U to 206Pb, with a half-life of 4.47 billion
years 235U to 207Pb, 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
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