Intro to Chem

CHEMISTRY

​An Introduction

What is matter?
What is energy?

Chemistry is the study of matter and energy.

What is Chemistry?

​All matter is comprised of tiny particles called atoms and molecules

​smallest units of elements

a group of atoms bonded together

ATOMIC MODEL THEORY
-"uncuttable" particles
- atomoz or atoms
- tiny, invisible particles
- separated by voids --
empty space

Democritus
460-370 BCE

- Earth is made up of matter

• Earth, Water, Air, Fire

Aristotle
384-322 BCE

Proposed Atomic Theory in 1894
- Atoms
- Element = a substance that contained only one particular type of atom
- All atoms are composed of a given set of subatomic particles: protons, neutrons, and electrons.

JOHN DALTON

PROTONS
- are positively charged particles, weighing 1 atomic mass unit (1.67x10^-24 grams) and located in the nucleus.

Neutrons
- are neutrally charged particles, weighing approximately 1 atomic mass unit and located in the nucleus.

Electrons

- negatively charged
- weighing zero atomic mass units
- located in the various orbitals of the energy levels outside the atomic nucleus.
- weighs 9.11x10^-28 grams.

What makes an atom of one element different from the atoms of every other element?

PERIODICITY

PERIODICITY

a repeating pattern of other characteristics of the elements

tendency to show a regular repeating pattern

• Russian scientist

• arranged the 60 elements he knew of at the time in order of each element's increasing mass

DMITRI MENDELEEVE

​Mendeleeve`s Original Table

1. Why were there blank spaces in Dmitri Mendeleeve`s table of elements?

2. Who is Henry Mosley?

3. What are Ions and Isotopes?

4. What are Protons and why are they important?

​The number of protons determine what kind of element the atom is, the neutrons determine if the atom is an isotope, and the electrons tell you if the atom is an ion or not.