Biology Chapter 2 - Chemistry for Biologists

What is Chemistry?

The study of the composition, structure and properties of matter and the changes that matter undergoes.

What is matter?

Matter has mass and occupies space (solid, liquid, gas)

5th century philosopher Democritus

Thought empty space was filled with indivisible particles called atoms

John Dalton

Proposed using the term atom in the 1800s

Niel’s Bohr

Atomic Structure 1913

Atom Composition

Atoms are composed of Protons (+), Electrons (-), and Neutrons (+/-)

What are elements?

Elements are pure substances that contain only one type of atom

Four main elements in our body

Hydrogen, Oxygen, Carbon, and Nitrogen (96.3%)

Atomic Number

Total number of protons in an atom

Mass Number

Total number of protons + neutrons

Isotopes

Atoms of a single element that differ by the number of neutrons