Midterm ReviewChapter 3 Pg 74-104

Atomic Theorypg 74-78 Atomic Theory – the idea that atoms

are the building blocks of all matter

Everything is made up of atoms

The Laws The law of conservation of mass – states

that mass is not created or destroyed in a reaction. The mass of the reactants is equal to the mass of

the products

N + O = NOMass of reactants Mass of ProductsN= 16 grams NO = ?O= 14 grams

The Laws Law of definite proportions – states

that two samples of a given compound are made of the same elements in exactly the same proportions by mass.

Example H2O (water) No matter how much water you have

(1g or 100g) it will always 89% O and 11% H

John Dalton Developed atomic theory

Proposed idea that elements are composed of only one kind of atom

Structure of Atomspg 79-89 Atoms can be divided into three

different particles Protons Neutrons Electrons

Atoms

Atoms Nucleus center that is composed of

protons and neutrons Nucleus has an overall positive charge

Electrons are in orbitals rotating around the nucleus

Subatomic Particles Protons – have mass of 1 amu and

positive charge (+1)

Neutrons – have mass of 1 amu and neutral charge

Electrons – are considered massless and have a negative charge (-1)

Atomic Number – the total number of protons in the nucleus of an atom

Mass Number – The sum of the number of protons and neutrons of the nucleus of an atom Protons + Neutrons = Mass Number

Average atomic mass – the weighted average of the masses of all naturally occurring isotopes of an element

Isotopes Isotopes – atoms that have the same

number of protons (same element) but differing numbers of neutrons

Different number of neutrons changes the atomic mass

Electron Configurationspg 90 - 99 Pauli Exclusion Principle – Electrons in the

same orbital have to spin in opposite directions

Aufbau Principle – Electrons fill orbitals starting with lowest energy level

Hund’s Rule – If energy levels have multiple orbitals, each orbital has to have one electron before any orbital has two electrons

https://www.youtube.com/watch?v=SoNIQjW5Zxs