The Evolution of Atomic Theory Chapter 3 The Evolution of Atomic Theory

The Structure of the Atom

The Structure of the Atom The “modern” atomic model… Describe the nucleus: What’s outside the nucleus? How are these particles important?

The Structure of the Atom How is it possible to have more than 100 different elements when they’re all made the same way? Protons? Examples:

The Structure of the Atom Atomic number (Z): How does the diagram show what “Z” means?

The Structure of the Atom Mass number: How does the diagram show what mass number means?

The Structure of the Atom Sketch a diagram of a neutral carbon atom in the following three ways, showing the correct numbers of protons, neutrons, and electrons (a) Make the mass number equal to 12 (b) Make the mass number equal to 13 Make the mass number equal to 14 What’s the same about all these? What’s different?

The Structure of the Atom Isotopes How does the diagram show that these atoms are isotopes?

The Structure of the Atom Isotope notation Shows both the mass number and the atomic number along with the element symbol Often, the atomic number is omitted as it is implied by the element symbol (since never changes) Can also be written…

The Structure of the Atom Isotopes How many carbon isotopes are there? Which one is most abundant? Describe the H isotopes in terms of mass and abundance…

The Structure of the Atom Identify an atom with a mass number of 16, containing 9 neutrons. Give the full atomic symbol for an atom with 16 neutrons and an atomic number of 15.

The Structure of the Atom What is atomic mass? How is it different than mass number? Explain the units…

The Structure of the Atom Describe and complete the sample calculation of weighted average atomic mass of carbon: The atomic mass of C on the periodic table is closest to the most abundant isotope’s mass. Why?

Dalton’s atomic theory All matter is made up of atoms Atoms are the fundamental unit of matter Atoms can neither be created nor destroyed. Atoms of a particular element are alike. Atoms of different elements are different. Atoms are hard spheres What’s needed change?

Atomic Theory The model proposed by J.J. Thomson is called the plum-pudding model…why? Two basic facts: What needed to change?

Atomic Theory Rutherford’s gold foil experiment Fired positive alpha particles at metal foil What happened? What does this tell us? Why did he “discover” the nucleus?

Rutherford’s Model of the Atom The Nucleus Rutherford’s Model of the Atom

The Structure of the Atom

By 1860, nearly 70 elements had been isolated and studied! Chemical Periodicity By 1860, nearly 70 elements had been isolated and studied! Mendeleev arranged them in order of their atomic mass What’s periodicity? Why is “it” called the PERIODIC Table?

Alkali Metals: K, Na, and Li Chemical Periodicity Alkali Metals: K, Na, and Li Describe their properties:

Elements across the 2nd row change… Chemical Periodicity Elements across the 2nd row change… From Li (a solid metal) to Ne (a gas) Why is this periodicity?

Predictions Using Mendeleev's table Chemical Periodicity Predictions Using Mendeleev's table How could we predict the properties of Ekasilicon? What is it really called?

The Modern Periodic Table

3.6 The Modern Periodic Table What are Periods of the Periodic Table?

3.6 The Modern Periodic Table What are Groups on the Periodic Table?

The Modern Periodic Table Sections of the Periodic Table Main-group elements— Transition metals— Lanthanides (rare earths) and actinides

3.6 The Modern Periodic Table Phase of elements: s, l or g

3.6 The Modern Periodic Table Metallic nature…

3.6 The Modern Periodic Table (Continued) Metals Nonmetals Metalloids

3.6 The Modern Periodic Table (Continued) Group Names… Representative Elements Five common names used…

Trends on the Periodic Table Atomic Radius:

Trends on the Periodic Table Ions: When an atom loses or gains at least 1 electron Negatively charged… Positively charged…

Trends on the Periodic Table Ion Formation… Anions: Explain how anions form based on what fluorine does

Trends on the Periodic Table Ion Formation… Cations: Explain how cations form based on what lithium does…

Ions and Ionization Ion notations Charges are shown as superscripts after symbol. + and – are used to show positive and negative charges For +1 and -1, the one is generally implied.

Ionization Energy Ionization energy Minimum amount of energy it takes to completely remove an electron from an atom What happens when atoms lose electrons? Why do metals have lower ionization energies than non metals?

Ionization Energy Ionization energy Describe the trend in ionization energy across a period: What happens in the next period? Why is this a periodic trend?