Atoms and the Periodic Table Chapter 17 Mrs. Chilton.
-
Upload
aidan-long -
Category
Documents
-
view
222 -
download
2
Transcript of 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
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
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