5_3 Electron Configurationx

Transcript 5_3 Electron Configurationx

Classwork:

Standard: 2e terms: 135 Article: 136 Mastering concept: 146(57-64) Practice Problems: 139(18-22), 141(23)

Homework:

Cornell notes: 5.3

sec. assessment: 141(24-26) 1

Section 5.3 Electron Configuration Section 5-3 Apply the Pauli exclusion principle, the aufbau principle, and Hund's rule to write electron configurations using orbital diagrams and electron configuration notation.

Define valence electrons, and draw electron-dot structures representing an atom's valence electrons.

electron: a negatively charged, fast-moving particle with an extremely small mass that is found in all forms of matter and moves through the empty space surrounding an atom's nucleus

Section 5.3 Electron Configuration (cont.) electron configuration aufbau principle Pauli exclusion principle Hund's rule valence electrons electron-dot structure A set of three rules determines the arrangement in an atom.

Section 5-3

Ground-State Electron Configuration Section 5-3 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.

Ground-State Electron Configuration (cont.) Section 5-3

Ground-State Electron Configuration (cont.) Section 5-3 The Pauli exclusion principle states that a maximum of two electrons can occupy a single orbital, but only if the electrons have opposite spins.

Hund’s rule states that single electrons with the same spin must occupy each equal energy orbital before additional electrons with opposite spins can occupy the same energy level orbitals.

Ground-State Electron Configuration (cont.) Section 5-3

Ground-State Electron Configuration (cont.) Noble gas notation uses noble gas symbols in brackets to shorten inner electron configuratio ns of other elements.

Section 5-3

Ground-State Electron Configuration (cont.) Section 5-3 The electron configurations (for chromium, copper, and several other elements) reflect the increased stability of half-filled and filled sets of s and d orbitals.

Valence Electrons Section 5-3 Valence electrons are defined as electrons in the atom’s outermost orbitals—those associated with the atom’s highest principal energy level.

Electron-dot structure consists of the element’s symbol representing the nucleus, surrounded by dots representing the element’s valence electrons.

Valence Electrons (cont.) Section 5-3

Electron Configuration Rules •

Aufbau:

electrons fill lowest Energy level 1 st •

Pauli:

only 2 electrons may share an atomic orbital, and only when they have opposite spins •

Hunds:

single electrons with the same spin must occupy each equal energy orbital before additional electrons with opposite spins can enter the same orbitals 12

Sub-shell

s p d f

#Orbits # Electrons

1 3 5 7 2 6 10 14 13

Mastering Concepts: 146(57-64) Electron Configurations

57. Explain the meaning of the aufbau principle as it applies to atoms with many electrons. (5.3) The aufbau principle describes the sequence in which an atom’s orbitals are filled with electrons.

58. In what sequence do electrons fill the atomic orbitals related to a sublevel? (5.3) Each orbital must contain a single electron before any orbital contains two electrons.

59. Why must the two arrows within a single block of an orbital diagram be written in opposite (up and down) directions? (5.3) Two electrons occupying a single atomic orbital must have opposite spins.

60. How does noble-gas notation shorten the process of writing an element’s electron 1 2

3 Na 4 [Ne] 3S 1 The noble-gas notation uses the bracketed symbol of the preceding noble gas in the periodic table to represent an atom’s inner electrons.

61. What are valence electrons? Valence electrons are the electrons in an atom’s outermost orbitals

Valence Electrons

61. How many of a magnesium atom’s 12 electrons are valence electrons? (5.3) 2

62. Light is said to have a dual wave-particle nature. What does this statement mean? (5.3) Light exhibits wavelike behavior in some situations and particlelike behavior in others.

63. Describe the difference between a quantum and a photon. (5.3) A quantum is the minimum amount of energy that can be lost or gained by an atom, while a photon is a particle of light that carries a quantum of energy.

64. How many electrons are shown in the electron-dot structures of the following elements? (5.3) a. Carbon 4 b. Iodine 7 c. Calcium 2 d. Gallium 3

Shorthand Configuration

A neon's electron configuration (1s 2 2s 2 2p 6 ) B third energy level

[Ne] 3s 1

C one electron in the s orbital D orbital shape

Na = [1s 2 2s 2 2p 6 ] 3s 1 electron configuration