Chemistry 100 Chapter 9 Electrons in Atoms and

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Chemistry 100 Chapter 9 Electrons in Atoms and the Periodic Table

Chemistry 100 Chapter 9 Electrons in Atoms and the Periodic Table

Structure of atom + - - - Rutherford’s model - e+ (Source of particles)

Structure of atom + - - - Rutherford’s model - e+ (Source of particles)

Electromagnetic radiation Energy is transferred by light.

Electromagnetic radiation Energy is transferred by light.

Electromagnetic radiation A wave characterized by three properties: Wavelength Wave: Frequency Speed

Electromagnetic radiation A wave characterized by three properties: Wavelength Wave: Frequency Speed

Electromagnetic radiation Wavelength (λ): distance from one wave peak to the next. λ =

Electromagnetic radiation Wavelength (λ): distance from one wave peak to the next. λ = 6× 10 -7 m λ = 1× 10 -7 m Frequency (ν): number of peaks that pass a given point in one second. c λ= ν c: speed of light = 3. 0 × 108 m/s

Electromagnetic radiation longer λ → lower ν shorter λ → higher ν λ Electromagnetic

Electromagnetic radiation longer λ → lower ν shorter λ → higher ν λ Electromagnetic spectrum

Electromagnetic radiation Photon: a stream of tiny packets of energy. (smallest unit of electromagnetic

Electromagnetic radiation Photon: a stream of tiny packets of energy. (smallest unit of electromagnetic radiation) shorter λ (higher ν) → higher energy longer λ (lower ν) → lower energy

Emission of energy by atoms Emitted photons (light) Energy of heat (or …) Flame

Emission of energy by atoms Emitted photons (light) Energy of heat (or …) Flame test

Emission of energy by atoms Excited states Only certain energy changes are allowed. Energy

Emission of energy by atoms Excited states Only certain energy changes are allowed. Energy levels are quantized. (lowest energy level) Only certain types of photons are produced.

Bohr model Electron orbits the nucleus in circles. Electrons are moving in only allowed

Bohr model Electron orbits the nucleus in circles. Electrons are moving in only allowed energy levels.

Wave mechanical model of atom Electron acts as a wave. Electron does not orbit

Wave mechanical model of atom Electron acts as a wave. Electron does not orbit the nucleus in circles. Electrons move randomly; however, there is more chance to find them close to nucleus.

n=4 Energy n=3 n=2 Principal energy levels n=1 ground state (lowest energy level) Sublevels:

n=4 Energy n=3 n=2 Principal energy levels n=1 ground state (lowest energy level) Sublevels: s p and can hold maximum 2 electrons p d s Orbital: is a region of space s p s s f d p d f Principal level 4 Principal level 3 Principal level 2 Principal level 1

s px py 4 s pz 4 p 3 s 4 d 3 p

s px py 4 s pz 4 p 3 s 4 d 3 p 2 s 1 S 2 S 3 S 3 d 2 p 1 s 4 f Principal level 4 Principal level 3 Principal level 2 Principal level 1

3 2 1 s, p, d s, p s

3 2 1 s, p, d s, p s

Pauli exclusion principle Orbital: is a region of space and can hold maximum 2

Pauli exclusion principle Orbital: is a region of space and can hold maximum 2 electrons magnetic field paired spins Two electrons can stay together even with their opposite charges.

Sublevels: s p d d f f Px Py Pz 2 2+2+2=6 2+2+2=10 2+2+2+2=14

Sublevels: s p d d f f Px Py Pz 2 2+2+2=6 2+2+2=10 2+2+2+2=14

1 1 s 2 2 2 s, 2 p 2+6=8 3 3 s, 3

1 1 s 2 2 2 s, 2 p 2+6=8 3 3 s, 3 p, 3 d 2 + 6 + 10 = 18 4 4 s, 4 p, 4 d, 4 f 2 + 6 + 10 +14 = 32 4 3 2 1 Principal energy level 3 d 4 s 3 p 3 s 2 p 2 s 1 s Orbitals Order of filling Orbitals Energy Level Maximum number of electrons

Electrons configuration: description of the orbitals that its electrons occupy. Orbital box diagrams H

Electrons configuration: description of the orbitals that its electrons occupy. Orbital box diagrams H (1) Electron configuration 1 s 1 s 2 He (2) 1 s 1 s 2 2 s 1 Li (3) 1 s 2 s 1 s 2 2 p 2 C (6) 1 s 2 s 2 px 2 py 2 pz

Noble gas notation 1 s 2 2 s 1 Li (3) 2 s 1

Noble gas notation 1 s 2 2 s 1 Li (3) 2 s 1 s [He] 2 s 1 F (9) 1 s 2 s 2 px 2 py 2 pz 1 s 2 2 p 5 [He] 2 s 2 2 p 5 Si (14) 1 s 2 s 2 px 2 py 2 pz 3 s 3 px 3 py 3 pz 1 s 2 2 p 6 3 s 2 3 p 2 [Ne] 3 s 2 3 p 2

Orbital filling order 1 s 2 s 2 p 3 s 3 p 3

Orbital filling order 1 s 2 s 2 p 3 s 3 p 3 d 4 s 4 p 4 d 4 f 5 s 5 p 5 d 5 f 6 s 6 p 6 d 6 f 1 s, 2 p, 3 s, 3 p, 4 s, 3 d, 4 p, 5 s, 4 d, 5 p, 6 s Hf (72): 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 10 5 p 6 6 s 2 4 f 14 5 d 2 [Xe] 6 s 2 4 f 14 5 d 2

Notice that Cr and Cu are exceptions to the usual trend. Having half-filled d

Notice that Cr and Cu are exceptions to the usual trend. Having half-filled d orbitals adds some stability. (You must be able to write the electron configurations for the first 4 periods. )

Valence level: outermost principle energy level Valence electrons: electrons in highest principal energy level.

Valence level: outermost principle energy level Valence electrons: electrons in highest principal energy level. Cl (17) 1 s 2 2 p 6 3 s 2 3 p 5 7 valence electrons Ar (18) 1 s 2 2 p 6 3 s 2 3 p 6 8 valence electrons C (6) 1 s 2 2 p 2 4 valence electrons Ne (10) 1 s 2 2 p 6 8 valence electrons Noble gases Filled valence level

Only valance electrons are involved in chemical bond and chemical reactions. Inner electrons (core

Only valance electrons are involved in chemical bond and chemical reactions. Inner electrons (core electrons) are not involved. Core electrons 1 s 2 2 p 6 3 s 2 3 p 6 Valance electrons Elements in same column (group) have the same number of electrons in their valance levels. Same chemical and physical properties.

Lewis dot structure H 1 A 2 A Cl C Li 3 A 4

Lewis dot structure H 1 A 2 A Cl C Li 3 A 4 A 5 A 6 A He 7 A 8 A Only for main-group element: # of group = # of valance electrons

Main groups elements s, p Transition elements s, p, d Inner transition elements s,

Main groups elements s, p Transition elements s, p, d Inner transition elements s, p, d, f

Atomic Size of atom: is the size of its outermost occupied orbital. d

Atomic Size of atom: is the size of its outermost occupied orbital. d

Ionization Energy Li + energy → Li+ + eion Ionization energy: the energy required

Ionization Energy Li + energy → Li+ + eion Ionization energy: the energy required to remove the most Ionization energy loosely held electron from an atom in the gaseous state. Ionization energy

Ions Electron Configuration • Ions have electron configurations where the neutral atom has lost

Ions Electron Configuration • Ions have electron configurations where the neutral atom has lost or gained electrons. Oxygen, O, 1 s 22 p 4 Oxide, O 2 -, 1 s 22 p 6 Sodium, Na, 1 s 22 p 63 s 1 sodium cation, Na+, 1 s 22 p 63 s 0 = 1 s 22 p 6 • Notice both O 2 - and Na+ have electron configurations identical to the noble gas neon.

Practice • What is the correct electron configuration for the element phosphorus? • What

Practice • What is the correct electron configuration for the element phosphorus? • What is the correct electron configuration for the element titanium? • Which noble gas electron configuration is exactly the same as the electron configuration for the Ca 2+ ion? • Which noble gas electron configuration is exactly the same as the electron configuration for the Se 2 - ion?