Unit 3- Properties of Atoms and Periodic Table Structure of the Atom Chemical Symbols Subatomic Particles

Chemical Symbols Chemical Symbols are used to represent element names Capitals matter! Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Co vs. CO Metal that forms bright blue solid compounds. Poisonous gas.

Atomic Components Every element is composed of one type of atom Atoms are the smallest pieces of matter that have properties of that element Composed of protons, neutrons and electrons Protons (p+): charge of 1+ Neutrons (n 0 ): no charge (neutral) Electrons (e-): charge of 1-

Atomic Components Protons and Neutrons are located in the nucleus of the atom The nucleus is positively charged It is surrounded by a cloud containing electrons Atoms of different elements differ in the number of protons

Atomic Components

Subatomic Particles Most of the atom’s mass. Atomic Number equals the # of... in a neutral atom NUCLEUS ELECTRONS PROTONS NEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE ATOM

Subatomic Particles Quarks: very small particles that make up protons and neutrons Scientists have confirmed 6 different quarks

Subatomic Particles To study quarks scientists accelerate particles and smash them into protons The collision breaks apart the proton

Atomic Models How small are atoms?? 24,400 atoms stacked on top of each other = the thickness of a piece of foil Scientists create scaled-up models to help visualize atoms Models are based on indirect evidence There have been many different models over the years

Electron Cloud Model The model now used is the Electron Cloud Model The electron cloud is the area where electrons are MOST likely to be found It is 100,000 times larger than the diameter of the nucleus Ex. Paperclip in a football stadium e/atom/ e/atom/

Orbital Region where there is 90% probability of finding an electron.  Can’t pinpoint the location of an electron.  Density of dots represents degree of probability.

Orbital Orbitals have different shapes.

Inside the Cloud Electrons are various distances away from the nucleus Closer energy levels have less energy and can hold fewer electrons Each energy level (n) can hold 2n 2 electrons. Energy LevelMax # of Electrons