Atoms and Electron Configurations

1. Atoms and Electron Configurations (revised)

2. Back in the day . . . • Many ancient scholars believed matter was composed of such things as earth, water, air, and fire. • Many believed matter could be endlessly divided into smaller and smaller pieces.

3. Relatively New Ideas • Dalton’s atomic theory easily explained conservation of mass in a reaction as the result of the combination, separation, or rearrangement of atoms.

4. Assessment Dalton’s theory also conveniently explained what? A.the electron B.the nucleus C.law of conservation of mass D.law of Democritus

5. What Do You Know? • What is the smallest particle of an element that retains its properties? • What subatomic particles make up atoms? • What are the charges of those particles? • Where are these particles located in the atom?

6. The Electron • Many years ago, J.J. Thompson studied a phenomenon that was the cathode ray. • Cathode rays are a steady stream of particles carrying a negative charge. • The particles carrying a negative charge are known as electrons.

7. The Electron (cont.) • Matter is neutral. • Using a Cathode Ray, Thomson discovered the electron and developed the plum pudding model

8. The Nucleus and the Proton • Ernest Rutherford discovered atoms were mostly empty space • Found that the positive charge of an atom is located in the nucleus • Called the positive charged particle the proton

9. The Neutron • James Chadwick received the Nobel Prize in 1935 for discovering the existence of neutrons, neutral particles in the nucleus which accounts for the remainder of an atom’s mass.

10. The Atom • All atoms =made of three fundamental subatomic particles: the electron, the proton, and the neutron. • Atoms are spherically shaped. • Atoms =mostly empty space, • electrons travel around nucleus • held by an attraction to the positively charged nucleus.

11. The Atom • Atom= smallest particle of an element that retains the properties of the element • Chemical behavior explained by considering only an atom's electrons.

12. Assessment Atoms are mostly ____. A.positive B.negative C.solid spheres D.empty space

13. Assessment What are the two fundamental subatomic particles found in the nucleus? A.proton and electron B.proton and neutron C.neutron and electron D.neutron and positron

14. Bohr's Model of the Atom (cont.)

15. The atom is a 3 demensional shape! • Even though this picture looks like caos. The electron are really in atomic orbitals!.

16. n specifies the atom’s major energy levels, called the principal energy levels. • Energy sublevels are contained within the principal energy levels.

17. Four types of sublevels • s are spherical holds 2 e- • p are dumbbell in shape holds 6 e- • d more complex in shape holds 10 e- • f more complex in shape holds 14 e-

18. s Orbitals • Groups IA and IIA fill the s-orbital • Spherical in shape • It can hold a maximum of two electrons

19. p Orbitals • Groups 3A - 8A fill the p-orbital • “Dumbbell shaped” • A p-orbital = 3 sub-orbitals – 1 along each axis • Each sub-orbital can hold a maximum of 2 electrons; • The p-orbital holds 6e-total

20. d orbitals • The transition metals (Group B elements) fill the d-orbital • The d-suborbitals (5) hold a maximum of two electrons=10e- total

22. Ground-State Electron Configuration • The arrangement of electrons in the atom is called the electron configuration. • The aufbau principle states that each electron occupies the lowest energy orbital available.

23. F orbitals

24. The Aufbau Principle • Each electron occupies the lowest energy orbital • Electrons are Lazy!!! • All orbitals related to an energy level are of equal energy. • Ex. The three 2p orbitals are the same energy level. All equivalent energy

25. Block Table • This shows the different blocks in the Periodic Table. • It also shows in what order to write electron configurations (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d,7p)

26. A maximum of two electrons may occupy a single orbital, but only if the electrons have opposite spins. Spin -- Electrons has an associated “spin,” either one way or the other, like a top. These spins are called “spin up” and “spin down.” Pauli Exclusion Principle Box = orbital Arrow = electron

27. Electrons, being unfriendly, fill up the empty orbitals before sharing orbitals. Similar to seats on a bus – on a bus, you sit alone, rather than with a stranger, if there is an option. Np1 Np2 Np3 Np4 Np5 Np6 The order of Things…

28. Single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals. Electrons are UNFRIENDLY Why? 1s2 2s2 2p3 1s2 2s2 2p3 Hund’s Rule Ex. Nitrogen: • 1s2 2s2 2p3 NOT

29. Brief Instructions • An electron configuration-- method of indicating the arrangement of electrons . • Consists of numbers, letters, and superscripts with the following format: • 1. A number indicates the energy level • 2. A letter indicates the type of orbital; s, p, d, f. • 3. A superscript indicates the number of electrons in the orbital. • Example: 1s2= 2electrons in the ‘s’ orbital of the 1st energy level. • The element is helium.

30. To write an electron configuration: • 1. Determine the total number of electrons to be represented. • 2. Use the Aufbau process to fill the orbitals with electrons. • That means fill the lowest energy orbitals first. • “Ground upwards.” • 3. The sum of the superscripts should equal the total number of electrons. • Example: 12Mg 1s2 2s2 2p6 3s2

31. Ground-State Electron Configuration (cont.)

32. Practice • Vanadium • 1s22s22p63s23p64s23d3 • Calcium • 1s22s22p63s23p64s2

33. Bromine • 1s22s22p63s23p64s23d104p5 • Rhenium • 1s22s22p63s23p64s23d104p65s24d105p66s24f145d5

34. Valence Electrons • Valence electronsare electrons in the atom’s outermost orbitals— • those associated with the atom’s highest principal energy level.

35. Ground-State Electron Configuration (cont.) • Noble gas notation uses noble gas symbols in brackets to shorten inner electron

36. Noble Gas Configuration • Strontium • [Kr]5s2 • Tungsten • [Xe]6s24f145d4