Atoms and Molecules Atom The smallest particle of

Atoms and Molecules

Atom � The smallest particle of an element ◦ Examples: �Hydrogen �Carbon �Chlorine �Titanium

The Atomic Model � Democritus (450 B. C. ) ◦ If you kept cutting a substance in half forever, eventually you would end up with an “uncuttable” particle. � John Dalton (1800) ◦ All substances are made of atoms ◦ Atoms of the same element are exactly alike, and atoms of different elements are different. � JJ Thompson (1897) ◦ Discovered electrons ◦ Developed “plum pudding” model

The Atomic Model � Ernest Rutherford (1911) ◦ Most of the atom’s mass is found in a region in the center called the nucleus � Neils Bohr (1913) ◦ Electrons travel around the nucleus in definite paths. � Erwin Schrodinger ◦ There are regions inside the atom where electrons are likely found

Nucleus � The central core of an atom, contains protons and usually neutrons

Proton � Small positively charged particles found in the nucleus of an atom

Neutron � Small uncharged particles found in the nucleus of an atom

Nuclear Energy � The potential energy stored in the nucleus of an atom Fusion Fission

Electron � Tiny, negatively-charged, high-energy particles that move around the outside of the nucleus

Electrical Energy � The energy of moving electrical charges � Charge- ◦ A definite amount of electricity, positive or negative

Element �A substance that cannot be broken down into any other substances

Atoms continued � Atomic Number= number of protons � Atomic Mass= number of protons + neutrons � # Electrons = # Protons

Calculations � Magnesium ◦ 12 protons ◦ 12 electrons ◦ 12 neutrons (24 -12=12) � Oxygen ◦ 8 protons ◦ 8 electrons ◦ 8 neutrons (16 -8=8)

Molecule �A particle made of two or more atoms bonded together

Chemical Bond � The force that holds the atoms together

Chemical energy � The potential energy stored in chemical bonds