Atoms and the Periodic Table

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Atoms and the Periodic Table
Chapter 17 Mrs. Chilton

Atoms Elements are made of particles called atoms
Atoms are the smallest pieces of matter that contain all the properties of a specific element Each element contains only one type of atom

Essential Question How do we know what the atom looks like when no one has ever seen it?

Inside the Atom Atoms are made up of smaller particles
These particles are found in different regions of the atom

Protons Positively charged particles found in nucleus of atom
Have an electrical charge of +1 Mass of 1 a.m.u. Composed of quarks

Neutrons Neutral particles found in nucleus of atom
Have no electrical charge Mass of 1 a.m.u. Composed of quarks

Nucleus The nucleus is the positively charged dense core in the center of the atom Contains 99.9% of mass of atom Houses protons and neutrons

Electrons Negatively charged particles found in electron cloud
Have an electrical charge of -1 Constantly moving around outside nucleus Have essentially no mass

Electron Cloud Region around nucleus Houses electrons

Time to Make a Foldable!

Time to Make a Foldable!

Atomic Models Have been revised many times to explain new discoveries
Democritus (4th century B.C.) thought the atom could not be split Theory was modified when subatomic particles were discovered

Newer Models Bohr’s Model (1913) revised earlier thoughts
Showed electrons moving in paths like planets Revised in 1925 Now electrons in cloud

Valence Electrons Electrons in the outermost energy level of an electron are called valence electrons These are the electrons furthest from the nucleus

Symbols Elements are listed by their chemical symbols
Symbols are usually either one capital letter like C for Carbon, or one capital and one lowercase letter like Ne for Neon

Periodic Table The periodic table gives much information we need to learn more about the atom of each element

Atomic Number Atomic number = # of protons in an atom
Whole number shown on periodic table Periodic table is arranged by atomic number

Atomic Mass Mass # = # p+ + # n0
The average atomic mass is the number at the bottom of this square Found by averaging the natural abundances of its isotopes Mass # = # p+ + # n0

Concept Map Complete this concept map:

Atom Math Atomic Number Symbol Element Name Atomic Mass

Atom Math Protons Electrons Protons Neutrons

Practice # n0 = Mass # - Atomic # Zn Oxygen Lithium 8 30 3 15.999
65.39 6.941 8 30 3 35 8 4 8 30 3 # n0 = Mass # - Atomic #

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