# Atomic Structure Chapter 4. Dalton’s Atomic Theory All elements are composed indivisible particles called atoms All elements are composed indivisible.

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Atomic Structure Chapter 4

Dalton’s Atomic Theory All elements are composed indivisible particles called atoms All elements are composed indivisible particles called atoms Atoms of the same element are identical and different from all other elements Atoms of the same element are identical and different from all other elements Atoms can physically mix together or combine chemically to form compounds Atoms can physically mix together or combine chemically to form compounds When atoms are separated, joined or rearranged a chemical reaction occurs; but atoms of one element never change into atoms of another element. When atoms are separated, joined or rearranged a chemical reaction occurs; but atoms of one element never change into atoms of another element.

Subatomic Particles Protons Protons Positive charge Positive charge Found in the nucleus Found in the nucleus Relative mass of 1 Relative mass of 1 Neutrons Neutrons NO charge NO charge Found in the nucleus Found in the nucleus Relative mass of 1 Relative mass of 1 Electrons Electrons Negative charge Negative charge Found outside the nucleus Found outside the nucleus Relative mass of 1/1840 Relative mass of 1/1840

Atomic Number vs. Mass Number Atomic Number = Protons in an atom Atomic Number = Protons in an atom Atomic Number = Electrons in an atom Atomic Number = Electrons in an atom Mass Number = Protons + Neutrons Mass Number = Protons + Neutrons

Complete the Table Element Atomic # ProtonsElectrons K1919 5 S16 V23 19 B55 1616 2323

How many protons, electrons and neutrons in each atom? Atomic # Mass#protonselectronsneutrons Beryllium (Be) 49 Neon(Ne)1020 Sodium (Na) 1123 445 101010 111112

Isotopes Elements with the same atomic number but different mass numbers Elements with the same atomic number but different mass numbers Same number of _________________ Same number of _________________ Different number of _______________ Different number of _______________ Examples: Examples: Carbon-12 Carbon-12 Carbon-13 Carbon-13

Atomic Mass Atomic Mass Unit (amu) – the mass of 1/12 the mass of a Carbon-12 atom Atomic Mass Unit (amu) – the mass of 1/12 the mass of a Carbon-12 atom Weighted average of the masses of all the isotopes of an element Weighted average of the masses of all the isotopes of an element

Calculating Atomic Mass Need to know: Need to know: Percent abundance of each isotope Percent abundance of each isotope Mass of each isotope Mass of each isotope 1 H 1 2 H 1 99.985% 1.0078 amu 0.015% 2.0141 amu.99985 x 1.0078.00015 x 2.0141

1 H 1 2 H 1.99985 x 1.0078 = 1.0076.00015 x 2.0141 =.000302 Add the relative masses together to get the average atomic mass Average atomic mass: 1.0076 +.000302 = 1.0079

History of the Periodic Table Mendeleev Mendeleev Tom Leher - Periodic Table Song

Periodic Table Groups Groups Periods Periods Metals Metals Alkali Metals Alkali Metals Alkaline Earth Metals Alkaline Earth Metals Non-metals Non-metals Noble-Gases Noble-Gases Halogens Halogens Metalloids Metalloids Transition Metals Transition Metals

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