Using the Periodic Table 6 Carbon C amu Atomic number- always a whole number, increases in order, represents the number of protons in each atom Atomic name, often in Latin, sometimes uses a common name, sometimes there are disagreements Atomic symbol – often, but not always, matches the name; Always capitalize the first (only the first ) letter Atomic mass- the mass of the atoms based on the average of all the most common isotopes

Atoms Chapter 6

Philosophy question: If you jump half-way across the room, and then continue jumping half-way, how many jumps until you reach the other side?

Aristotle, the famous Greek philosopher and scientist, argued that a substance could be divided again and again, forever getting smaller and smaller pieces During his time people believed the universe was made of four elements; fire, water, earth and air.

The idea of “uncuttable” particles was first suggested by Democritus around 440 B.C. “Atomos” means indivisible

Antoine Lavoisier Considered the Father of Chemistry due his extensive research and many experiments, including how things burn (food, wood etc) and the Law of Conservation of Mass Executed in 1794 during the French revolution

Section 1 Atomic Theory Atomic Theory (by John Dalton) published in 1803 –All substances are made from atoms. Atoms cannot be created, divided or destroyed. –Atoms of the same element are exactly alike. –Atoms can join together to form new substances.

Parts of the Atom ParticleChargeLocationSize Proton PositiveIn the nucleus1 a.m.u. Neutron No charge (neutral) In the nucleus Almost 1 a.m.u. Electron Negative Outside the nucleus, orbiting at nearly the speed of light Very tiny, 1/1000 th a.m.u.

Structure of the Atom Protons –Positively charged –Found in the nucleus of the atom (center) –Mass of 1 amu (atomic mass unit) –Gives the element its atomic number on the periodic table #1 (hydrogen) has 1 proton #4 (beryllium) has 4 protons + Protrons were discovered by Ernest Rutherford in 1911 and he discovered the empty space within an atom in 1909

Neutrons –Neutral charge ( no charge) –Found in the nucleus (center) –Mass slightly smaller than a proton, still considered 1 amu –Protons + Neutrons  atomic mass (rounded to the nearest whole number) N

Electrons –Negatively charged particles –Found outside the nucleus, moving at nearly the speed of light, in specific levels –Most commonly atoms are neutral particles having equal numbers of protons and electrons –Very small ( about 1/1000 th of a proton) Proton Neutron Electron Electrons were discovered by J.J. Thompson in 1897

* In 1913 Niels Bohr suggested that electrons travel in specific paths called Electron Shells Each level can only contain a certain number of electrons before it is full Each level will fill completely before electrons go to the next level Lower levels fill first

Isotope –Atoms can often be found with different numbers of neutrons Some atoms have only one stable isotope, others have several Averaging the masses of the isotopes in their correct percentages gives the exact atomic mass for each element Unstable isotopes break down (radioactive decay) Hydrogen (H-1), most common 99.9% tritium (H-3), least common, radioactive deuterium (H-2),

Different isotopes are identified by their mass numbers For example 12 C 13 C 14 C 6 protons + 6 neutrons 6 protons + 7 neutrons 6 protons + 8 neutrons Mass number is the protons + neutrons Sometimes written C-12, C-13, C-14

Calculating Atomic Mass Using Isotopes Determine the mass of each isotope based on its abundance (percent of each isotope found) –Remember, convert percents into decimals –Multiply by the mass number of the isotope Cl-3576% 35 x 0.76 = 26.6 Cl-3724% 37 x 0.24 = = amu * Your calculated answer should be very close to the mass on the periodic table Sample of chlorine Actual mass = amu

Slides 1 – 15 for honors Slides for reg

Atoms Chapter 6

Section 1 Atomic Theory Atomic Theory (by John Dalton) published in 1803 –All substances are made from atoms. Atoms cannot be created, divided or destroyed. –Atoms of the same element are exactly alike. –Atoms can join together to form new substances.

Parts of the Atom ParticleChargeLocationSize Proton PositiveIn the nucleus1 a.m.u. Neutron No charge (neutral) In the nucleus Almost 1 a.m.u. Electron Negative Outside the nucleus, orbiting at nearly the speed of light Very tiny, 1/1000 th a.m.u.

Structure of the Atom Protons –Positively charged –Found in the nucleus of the atom (center) –Mass of 1 amu (atomic mass unit) –Gives the element its atomic number on the periodic table #1 (hydrogen) has 1 proton #4 (beryllium) has 4 protons + Protrons were discovered by Ernest Rutherford in 1911 and he discovered the empty space within an atom in 1909

Neutrons –Neutral charge ( no charge) –Found in the nucleus (center) –Mass slightly smaller than a proton, still considered 1 amu –Protons + Neutrons  atomic mass (rounded to the nearest whole number) N

Electrons –Negatively charged particles –Found outside the nucleus, moving at nearly the speed of light, in specific levels –Most commonly atoms are neutral particles having equal numbers of protons and electrons –Very small ( about 1/1000 th of a proton) Proton Neutron Electron Electrons were discovered by J.J. Thompson in 1897

* In 1913 Niels Bohr suggested that electrons travel in specific paths called Electron Shells Each level can only contain a certain number of electrons before it is full Each level will fill completely before electrons go to the next level Lower levels fill first