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Ch. 3 – Atoms: The Building Blocks of Matter. An atom is the smallest matter that can’t be divided into smaller matter. What is an atom made up of? Nucleus Proton – positive charge Neutron – neutral charge Electron clouds (energy levels) Electrons – negative charge
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Ch. 3 – Atoms: The Building Blocks of Matter • An atom is the smallest matter that can’t be divided into smaller matter. • What is an atom made up of? • Nucleus • Proton – positive charge • Neutron – neutral charge • Electron clouds (energy levels) • Electrons – negative charge • Atom is Greek for indivisible
Dalton’s Theory Explains the make up of an atom. • Nucleus Protons & Neutrons • Electron Clouds Electrons • Bohr’s Model • Show’s the make up of an atom.
Atoms of different elements may combine to form chemical compounds. • In chemical reactions atoms are either combined, separated, or rearranged • Atoms cannot be created nor destroyed. • Each element can have more than 1 atom. • Ex. Cl2 • MASS # - ATOMIC # = NEUTRONS
Atoms of the same element may have different masses. These are called isotopes. • Ex. Hydrogen has 3 isotopes Protium, deuterium, tritium. • What does the atomic number tell you? • Number of protons in each atom of an element. • What does the mass number tell you? • Total number of protons and neutrons in the nucleus of an atom. • If an element has isotopes for that element they are called nuclides.
An atomic mass unit is a standard unit used for comparison. • Carbon has exactly 12 atomic mass units (U) and is used as a standard for comparison. • Each element on the periodic table has an average atomic mass. • Why do you suppose it is an average? • Average atomic mass is the weighted average of the atomic masses of the naturally occurring isotopes of an element. • Ex. Cu 69.17% is Cu – 63; 30.83% is Cu – 65.
Mole, Molar Mass, and Avogadro’s number all help describe an element. • CD ROM • Mole – Roughly the mass of a substance that is has 6.02 x 1023 particles (atoms or molecules). • All of the average atomic masses on the periodic table is equal to 1 mole (mol.). • Ex. B 10.81g = 1 mol. • Ex. Zn 65.39g = 1 mol.
Avogadro’s number is 6.02 X 1023 particles. • The number of particles (atoms or molecules) in exactly one mole is always 6.02 X 1023. • Ex. B 10.81g = 6.02 X 1023. • Ex. Zn 65.39g = 6.02 X 1023. • Molar mass – the mass in grams of one mol. Of a pure substance. • Basically the average atomic mass in grams. • Ex. B 10.81g = 1 mol. = 6.02 X 1023. • Ex. Zn 65.39g = 1 mol. = 6.02 X 1023.
The molar mass of all elements will always contain the same number of atoms, which is 6.02 X 1023. • Which atoms are heavier? • Do the heavier atoms have more atoms in one mole? • Pg. 90 • Sample Problems from pg. 82-85.