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