ICP Mr. Patel SWHS

Learn Major Elements The Atom Subatomic Particles Modern Atomic Theory Organizing the Elements Periodic Table Classifying Elements Atomic Models

Atom – the smallest particle of an element that retains its identity Can not see with naked eye Nanoscale (10 -9 m) Seen with scanning tunneling electron microscope

Democritus was a Greek to first come up with idea of an atom. His belief: atoms were indivisible and indestructible. = WRONG! Atom comes from “atmos” - indivisible

2000 yrs later, John Dalton used scientific method to transform Democritus’s idea into a scientific theory Dalton put his conclusions together into his Atomic Theory (4 parts)

1. All elements are composed of indivisible atoms.

2. Atoms of the same element are identical. Atoms of different elements are different

3. Atoms of different elements can chemically combine in whole number ratios.

4. Atoms of one element can never be changed to another element

Particle with negative charge Discovered by J.J. Thomson Used cathode ray (electron) beam and a magnet/charged plate. Millikan found the charge and mass

An atom is electrically neutral If there is a negative particle then there must be positive particle Proton – particle with positive charge Chadwick discovered neutron – neutral charge

Electrons distributed in a sea of positive charge Plum Pudding Model

The nucleus is the central part of the atom containing protons and neutrons Positive charge Most of the mass Electrons are located outside the nucleus Negative charge Most of the volume

An element is defined only by the number of protons it contains Atomic Number – number of protons Number of protons = number of electron For a neutral element

1. Zinc (Zn) 2. Iron (Fe) 3. Carbon (C) 4. Uranium (U)

Nucleus contains most of the mass Mass Number – total protons and neutrons Number of neutron = Mass # – Atomic #

1. Lithium (MN = 7) 2. Nitrogen (MN = 14) 3. Fluorine (MN = 19) ** MN = Mass Number 1. 3 p +, 3 e -, 4 n p +, 7 e -, 7 n p +, 9 e -, 10 n 0

Different element: different number of protons Ions – same number of proton, different number of electrons Isotope – same number of proton, different number of neutrons Different Mass Numbers

Nuclear Notation Write the element symbol On left side, superscript = Mass Number On left side, subscript = Atomic Number Isotope –Hyphen Notation Write full name of element On right side, put a dash On right side put Mass Number after dash Hydrogen - 3

Atomic Mass Unit (amu) – one-twelfth of the mass of the carbon-12 atom Different isotopes have different amu (mass) and abundance (percentage of total) Atomic Mass – weighted average mass of the naturally occurring atoms. Isotope Mass Isotope Abundance

Because abundance is considered, the most abundant isotope is typically the one with a mass number closest to the atomic mass. Example, Boron occurs as Boron-10 and Boron-11. Periodic Table tells us Born has atomic mass of amu. Boron-11 must be more abundant