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Chapter 4 Atomic Structure 4.2 Structure of the Nuclear Atom

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1 Chapter 4 Atomic Structure 4.2 Structure of the Nuclear Atom
4.1 Defining the Atom 4.2 Structure of the Nuclear Atom 4.3 Distinguishing Among Atoms Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

2 Early Models of the Atom
Dalton’s Atomic Theory – True or False? Elements are composed of tiny indivisible atoms. Atoms of the same element are identical. Atoms of one element differ from those of another element. Atoms of different elements can physically mix or chemically combine in simple whole-number ratios to form compounds. Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

3 Early Models of the Atom
Dalton English chemist & school teacher (1766 – 1864) Used experimental methods to develop scientific theory Democritus Greek philosopher (460 BC –370 BC) Reasoned atoms were indivisible & indestructible Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

4 In 1897, J. J. Thomson discovered the electron.
Subatomic Particles Electrons In 1897, J. J. Thomson discovered the electron. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

5 Thomson’s atomic model
Plum Pudding Model Thomson’s atomic model Electrons stuck in a lump of positive charge, similar to raisins stuck in dough. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

6 Rutherford’s Gold-Foil Experiment
The Atomic Nucleus Rutherford’s Gold-Foil Experiment Beam of alpha particles directed at sheet of gold foil. Some particles bounced off of gold foil. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

7 The Rutherford Atomic Model Protons and neutrons are in the nucleus
The Atomic Nucleus The Rutherford Atomic Model Protons and neutrons are in the nucleus Electrons around nucleus occupy almost all of the volume of the atom Did NOT explain chemical properties of elements Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

8 Key Concepts If an atom were the size of a football stadium, the nucleus would be the size of a marble Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

9 Energy Levels in Atoms The Bohr Model Each possible electron orbit has a fixed energy known as an energy level. Quantum of Energy Amount of energy required to move an electron from one energy level to another. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

10 Each energy level can hold a specific number of electrons.
Energy Levels in Atoms Each energy level can hold a specific number of electrons. Maximum # electrons = 2n2 Energy Level (n) Max # Electrons 1 2 8 3 18 4 32 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11 It is the same number as the period (row) on periodic table
Atomic Orbitals Energy Level (n) It is the same number as the period (row) on periodic table The bigger the energy level, the further the electrons are from the nucleus, and the more energy they have Also called Principal Quantum Number Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

12 Energy Levels in Atoms The Bohr Model Ground state - electron occupies lowest possible energy level Excited state - electron absorbs energy and jumps to a higher energy level When electron returns to ground state, it releases energy in the form of light. Emission Line Spectra Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

13 The Quantum Mechanical Model
Electron does not have an exact orbit. Atomic Orbital – region of space where there is a high probability of finding an electron. Electron cloud Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

14 Each energy level contains sublevels
Atomic Orbitals Sublevels Each energy level contains sublevels Sublevels contain orbitals of different shapes and energies (s,p,d, or f) Each orbital can hold 2 electrons. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

15 Atomic Orbitals Sublevels # of sublevels within an energy level is equal to the principle quantum number For example, n = 1 has 1 sublevel n = 2 has 2 sublevels Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

16 There can be several orbital configurations within a sublevel
Atomic Orbitals Sublevels There can be several orbital configurations within a sublevel s – sublevel contains 1 orbital p – sublevel contains 3 orbitals d – sublevel contains 5 orbitals f – sublevel contains 7 orbitals Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

17 Atomic Orbitals Summary of Principal Energy Levels and Sublevels
Number of sublevels Type of sublevel (n2) Maximum number of electrons (2n2) n = 1 1 1s (1 orbital) 2 n = 2 2s (1 orbital), 2p (3 orbitals) 8 n = 3 3 3s (1 orbital), 3p (3 orbitals), 3d (5 orbitals) 18 n = 4 4 4s (1 orbital), 4p (3 orbitals), 4d (5 orbitals), 4f (7 orbitals) 32 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

18 Quantum Numbers

19 Electron Configurations
Describes location of electrons in an atom Composed of energy levels, sublevels, and electrons Looks like… Titanium: 1s22s22p63s23p64s23d2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

20 Early Models of the Atom
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.


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