Unit 8: Ch. 4 & 5 ATOMIC STRUCTURE *An atom is the smallest particle of an element that retains its identity in a chemical reaction. LecturePLUS Timberlake

DEMOCRITUS’S ATOMIC PHILOSOPHY *He believed that atoms were indivisible and indestructible. His ideas agreed with later scientific theory but they did not explain chemical behavior. *His ideas were faulty because they lacked experimental evidence. LecturePLUS Timberlake

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LecturePLUS Timberlake JOHN DALTON John Dalton was an English chemist and schoolteacher. His ideas came more than 2000 years after Democritus. ***He used experimentation to change Democritus’s theory into a legitimate scientific theory. LecturePLUS Timberlake

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DALTON’S ATOMIC THEORY *All elements are composed of tiny indivisible particles called atoms. *Atoms of the same element are identical and atoms of different elements are different. LecturePLUS Timberlake

DALTON’S ATOMIC THEORY continued *Atoms of different elements can physically mix together or they can chemically combine to form compounds. *Chemical reactions occur when atoms are separated, joined or rearranged. LecturePLUS Timberlake

LecturePLUS Timberlake THE SIZE OF ATOMS *Individual atoms are very small. The radii of atoms are between 10-11 m & 10-10 m *Despite their small size, individual atoms can be seen with scanning tunneling microscopes. LecturePLUS Timberlake

LecturePLUS Timberlake element At # p+ n mass # Page 3 C 12 8 8 H 1 6 14 H 2 N 14 1 2 92 146 Cs 82 11 12 LecturePLUS Timberlake

LecturePLUS Timberlake symbol At # p+ n e At mass # Page 4 C 8 12 24 31 40 40 89 30 35 42 98 W 183 105 71 95 243 Cr 27 LecturePLUS Timberlake

LecturePLUS Timberlake element p+ n e At mass At # Page 5 lithium carbon chlorine silver lead calcium tantalum radium samarium uranium LecturePLUS Timberlake