Atoms and the Periodic Table

Chapter 17Mrs. 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

• 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 NumberSymbol

Element Name

Atomic Mass

Atom Math

Protons Electrons

Protons Neutrons

Practice

30815.9998

88

Zn

Oxygen

65.393035

30

Lithium

36.9413

43

# n0 = Mass # - Atomic #