DO NOW Pick up notes handout and periodic table. Pick up small white paper and do this below on it… A B C PARTS OF THE ATOM On a piece of paper, write A-E. Write the name of the part of the atom next to each correct letter (see drawing to the right), and turn it in. D E

THE ATOM

NUCLEUS Center of the atom 99.9% of the mass Contains two particles – protons and neutrons Has a positive charge

SUBATOMIC PARTICLES PROTON, p+ Positive charge. Located in the nucleus. All protons are identical, regardless of the element. Mass = ONE amu The number of protons determines the element. If the number of protons changes, so does the element.

SUBATOMIC PARTICLES NEUTRON, no Neutral – no charge Located in the nucleus. All neutrons are identical, regardless of the element. Mass = ONE amu

ELECTRON CLOUD Space where the electron is most likely to be. Surrounds the nucleus. Has no definite edge.

SUBATOMIC PARTICLES ELECTRON, e- Negative charge. Located outside the nucleus in the electron cloud. Mass =1/1840 amu In a neutral atom, the number of protons equals the number of electrons.

PROTONS AND NEUTRONS PROTON NEUTRON

QUARKS AND LEPTONS

IMPORTANT NUMBERS ATOMIC NUMBER, Z equals the number of protons. Determines the identity of the element.

IMPORTANT NUMBERS ATOMIC MASS The average of the masses of the isotopes of an atom. The mass on the periodic table (bottom number).

IMPORTANT NUMBERS MASS NUMBER, A the number of neutrons and protons (nucleons); take the whole number of the atomic mass.

HOW DO YOU DETERMINE THE NUMBER OF… Number of Protons: The atomic number. Number of Neutrons: Mass number minus atomic number. Number of Electrons: Same as the number of protons in a neutral atom.

REMEMBER The atomic number of an element NEVER changes. The number of protons in an element is ALWAYS the same. The number of neutrons and electrons can change and the element is still the same element.

PRACTICE How many protons and electrons are present in a vanadium atom? How many protons and electrons are present in a nitrogen atom? How many protons and electrons are present in an argon atom? What is the name of the element that has atoms that contain 5 protons?

PRACTICE How many protons, neutrons, and electrons are present in zirconium-91? How many protons, neutrons, and electrons are present in cesium-140? What is the atomic number and the mass number for the element with 27 protons and 32 neutrons? What is the atomic number and mass number for the element with 84 protons and 125 neutrons?

CALCULATING ATOMIC MASS The atomic mass on the periodic table is the average of the masses of the isotopes of an element. You must learn to calculate them.

PRACTICE The atomic mass of iridium-191 is 191.0 amu and iridium-193 is 193.0 amu. The percentage abundance for each is 37.58% (iridium-191) and 62.62% (iridium-193). Calculate the average atomic mass of iridium. Show your work.

TO DO Atomic Structure and Mass handout due tomorrow.